Merge branch '1492-send-after-previews-loaded' into 'master'

...a/org/briarproject/briar/android/blog/ReblogFragment.java

...riarproject/briar/android/blog/WriteBlogPostActivity.java

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

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

...iar/android/introduction/IntroductionMessageFragment.java

...iarproject/briar/android/threaded/ThreadListActivity.java

.../briarproject/briar/android/view/CompositeSendButton.java

...ava/org/briarproject/briar/android/view/ImagePreview.java

.../briarproject/briar/android/view/ImagePreviewAdapter.java

...iarproject/briar/android/view/ImagePreviewViewHolder.java

...g/briarproject/briar/android/view/LargeTextInputView.java

...rproject/briar/android/view/TextAttachmentController.java

...va/org/briarproject/briar/android/view/TextInputView.java

...g/briarproject/briar/android/view/TextSendController.java

briar-android/src/main/res/layout/text_input_view.xml

briar-android/src/main/res/layout/text_input_view_large.xml

...ndroid/src/main/res/layout/view_composite_send_button.xml