Fix back button after disconnect

After disconnecting the user needed to press the back button
multiple times to exit the app, because instead of just finising
the app started a new MainActivity.

Adittionally, if the user entered the app by pressing the
notification, the back stack was lost.

Thanks to Toastdeib for reporting this.
Moved Autocomplete to menu

By registering a context menu on the chat input the default menu
has been disabled. This is confusing for users, because e.g.
paste is no longer easily accesible.
Instead of registering a context menu for autocomplete, it is now
accessible as part of the menu dropdown.
Drinks are now properly pluralized
Fixed Lint warnings