Improve conversation screen graphics with less padding

Also replace more raster graphics with vector graphics.

briar-android/res/drawable/alerts_and_states_error.xml

+<vector android:alpha="0.54" android:height="24dp"
+    android:viewportHeight="24.0" android:viewportWidth="24.0"
+    android:width="24dp" xmlns:android="http://schemas.android.com/apk/res/android">
+    <path android:fillColor="#FF000000" android:pathData="M15.73,3L8.27,3L3,8.27v7.46L8.27,21h7.46L21,15.73L21,8.27L15.73,3zM12,17.3c-0.72,0 -1.3,-0.58 -1.3,-1.3 0,-0.72 0.58,-1.3 1.3,-1.3 0.72,0 1.3,0.58 1.3,1.3 0,0.72 -0.58,1.3 -1.3,1.3zM13,13h-2L11,7h2v6z"/>
+</vector>

briar-android/res/drawable/message_notification_icon.xml

+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+        android:width="24dp"
+        android:height="24dp"
+        android:viewportWidth="24.0"
+        android:viewportHeight="24.0">
+    <path
+        android:fillColor="#FFFFFFFF"
+        android:pathData="M20,4L4,4c-1.1,0 -1.99,0.9 -1.99,2L2,18c0,1.1 0.9,2 2,2h16c1.1,0 2,-0.9 2,-2L22,6c0,-1.1 -0.9,-2 -2,-2zM20,8l-8,5 -8,-5L4,6l8,5 8,-5v2z"/>
+</vector>

briar-android/res/drawable/navigation_accept.xml

+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+        android:width="24dp"
+        android:height="24dp"
+        android:alpha="0.54"
+        android:viewportHeight="24.0"
+        android:viewportWidth="24.0">
+	<path
+		android:fillColor="#FF000000"
+		android:pathData="M9,16.17L4.83,12l-1.42,1.41L9,19 21,7l-1.41,-1.41z"/>
+</vector>

briar-android/res/layout/list_item_introduction_in.xml

@@ -14,29 +14,29 @@
 		android:layout_width="wrap_content"
 		android:layout_height="wrap_content"
 		android:layout_gravity="left|start"
-		android:background="@drawable/notice_in"
 		android:layout_marginLeft="@dimen/message_bubble_margin_tail"
-		android:layout_marginRight="@dimen/message_bubble_margin_non_tail">
+		android:layout_marginRight="@dimen/message_bubble_margin_non_tail"
+		android:background="@drawable/notice_in">
 
 		<TextView
 			android:id="@+id/introductionText"
 			android:layout_width="wrap_content"
 			android:layout_height="wrap_content"
 			android:minWidth="80dp"
+			android:textColor="@color/briar_text_secondary"
 			android:textIsSelectable="true"
 			android:textSize="@dimen/text_size_medium"
 			android:textStyle="italic"
-			android:textColor="@color/briar_text_secondary"
 			tools:text="@string/introduction_request_received"/>
 
 		<TextView
 			android:id="@+id/introductionTime"
 			android:layout_width="wrap_content"
 			android:layout_height="wrap_content"
-			android:layout_marginTop="@dimen/message_bubble_timestamp_margin"
 			android:layout_alignEnd="@+id/introductionText"
 			android:layout_alignRight="@+id/introductionText"
 			android:layout_below="@+id/declineButton"
+			android:layout_marginTop="@dimen/message_bubble_timestamp_margin"
 			android:textColor="@color/private_message_date"
 			android:textSize="@dimen/text_size_tiny"
 			tools:text="Dec 24, 13:37"/>
@@ -56,8 +56,8 @@
 			style="@style/BriarButtonFlat.Negative"
 			android:layout_width="wrap_content"
 			android:layout_height="wrap_content"
-			android:layout_marginBottom="-15dp"
 			android:layout_below="@+id/introductionText"
+			android:layout_marginBottom="-15dp"
 			android:layout_toLeftOf="@+id/acceptButton"
 			android:layout_toStartOf="@+id/acceptButton"
 			android:text="@string/decline"/>

briar-android/res/layout/list_item_msg_in.xml

@@ -14,9 +14,9 @@
 		android:id="@+id/msgBody"
 		android:layout_width="wrap_content"
 		android:layout_height="wrap_content"
+		android:textColor="@color/briar_text_primary"
 		android:textIsSelectable="true"
 		android:textSize="@dimen/text_size_medium"
-		android:textColor="@color/briar_text_primary"
 		tools:text="Short message"/>
 
 	<TextView

briar-android/res/layout/list_item_msg_out.xml

@@ -11,9 +11,9 @@
 		android:layout_width="wrap_content"
 		android:layout_height="wrap_content"
 		android:layout_gravity="right|end"
-		android:background="@drawable/msg_out"
 		android:layout_marginLeft="@dimen/message_bubble_margin_non_tail"
-		android:layout_marginRight="@dimen/message_bubble_margin_tail">
+		android:layout_marginRight="@dimen/message_bubble_margin_tail"
+		android:background="@drawable/msg_out">
 
 		<TextView
 			android:id="@+id/msgBody"
@@ -28,11 +28,11 @@
 			android:id="@+id/msgTime"
 			android:layout_width="wrap_content"
 			android:layout_height="wrap_content"
-			android:layout_marginTop="@dimen/message_bubble_timestamp_margin"
 			android:layout_alignParentLeft="true"
 			android:layout_alignParentStart="true"
 			android:layout_below="@+id/msgBody"
-			android:singleLine="true"
+			android:layout_marginTop="@dimen/message_bubble_timestamp_margin"
+			android:maxLines="1"
 			android:textColor="@color/private_message_date_inverse"
 			android:textSize="@dimen/text_size_tiny"
 			tools:text="Dec 24, 13:37"/>

briar-android/res/values/dimens.xml

@@ -36,9 +36,9 @@
 	<dimen name="unread_bubble_padding_horizontal">6dp</dimen>
 	<dimen name="unread_bubble_size">19dp</dimen>
 
-	<dimen name="message_bubble_margin_tail">14dp</dimen>
-	<dimen name="message_bubble_margin_non_tail">51dp</dimen>
-	<dimen name="message_bubble_timestamp_margin">15dp</dimen>
+	<dimen name="message_bubble_margin_tail">3dp</dimen>
+	<dimen name="message_bubble_margin_non_tail">30dp</dimen>
+	<dimen name="message_bubble_timestamp_margin">7dp</dimen>
 	<dimen name="forum_nested_line_width">2dp</dimen>
 	<dimen name="forum_nested_indicator">24dp</dimen>
 	<dimen name="forum_avatar_size">20dp</dimen>