Merge branch '1473-display-multiple-images' into 'master'

...ject/briar/android/conversation/AttachmentController.java

...ject/briar/android/conversation/ConversationActivity.java

...oject/briar/android/conversation/ConversationAdapter.java

...riar/android/conversation/ConversationItemViewHolder.java

...r/android/conversation/ConversationMessageViewHolder.java

...ar/android/conversation/ConversationNoticeViewHolder.java

...r/android/conversation/ConversationRequestViewHolder.java

...ect/briar/android/conversation/ConversationViewModel.java

...briarproject/briar/android/conversation/ImageAdapter.java

...oject/briar/android/conversation/ImageItemDecoration.java

...arproject/briar/android/conversation/ImageViewHolder.java

...iarproject/briar/android/conversation/ImageViewModel.java

.../android/conversation/glide/BriarImageTransformation.java

...droid/conversation/glide/CustomCornersTransformation.java

.../briarproject/briar/android/conversation/glide/Radii.java

...ain/java/org/briarproject/briar/android/util/UiUtils.java

.../src/main/res/layout/list_item_conversation_msg_image.xml

...main/res/layout/list_item_conversation_msg_image_text.xml

...oid/src/main/res/layout/list_item_conversation_msg_in.xml

...id/src/main/res/layout/list_item_conversation_msg_out.xml