* General (makeshift): Set default first-tab to be profile, adjust search button appearance logic, add fragment labels
* DM inbox items: Adjust group chat avatar sizes, reinstate unread indicators
* DM thread: Swap buttons per spirit of #122
* Profile: Fix story fetcher logic
* Story: Fix bug where first story can't scroll to next user, unify subtitle to timestamp, swap buttons per #122
* Comment: Unfocus replying comment when X is pressed
This commit sets up the base for future enhancements in direct messages. The changes are:
1. Introducing fragments and navigation using androidx.navigation.fragment.NavHostFragment.
2. Using ListAdapter and LiveData for the RecyclerViews.
3. Fixes a bug where a single direct message was lost when querying older messages.