Group strings and remove unused resources

Closes #342

briar-android/AndroidManifest.xml

@@ -277,7 +277,7 @@
 
 		<activity
 			android:name=".android.SettingsActivity"
-			android:label="@string/settings_title"
+			android:label="@string/settings_button"
 			android:parentActivityName=".android.NavDrawerActivity">
 			<meta-data
 				android:name="android.support.PARENT_ACTIVITY"

briar-android/res/drawable-v21/round_button.xml

-<?xml version="1.0" encoding="utf-8"?>
-<!--
-	A FAB does not work, because even with fabSize="mini" it will be too big due to shadow drawing
-	on lower API levels
--->
-<ripple
-	xmlns:android="http://schemas.android.com/apk/res/android"
-	android:color="@color/briar_primary_dark">
-
-	<item>
-		<shape android:shape="oval">
-			<solid android:color="@color/briar_primary"/>
-		</shape>
-	</item>
-
-</ripple>
\ No newline at end of file