Gallery2: Fix various issues and glitches

* Remove unnecessary navbar toggles, and add missing ones
* Modify picker dialog style
* Fix editor bottom bar glitch with API 25
* Update main gallery layout so new bottom navigation works
  properly, and fix various other issues related to it
* Don't hide action bar in editor when adjusting effects, so
  we can see the values we adjust
* Update toolbar layout

Change-Id: I2a8f0b57ec874434c0fd0bb55de784b5d8379091