[geary] (20 commits) ...Merge branch 'adaptive' into 'mainline'

[Michael Gratton <mjog src gnome org>]

Summary of changes:

  a1f74d2... Drop saving the paned width
  fb311e1... Drop the 2-panes mode
  850efb7... application-main-window: Move the conversations searchbar
  94ab7e5... main-toolbar: Split the folder header
  7d4a61d... main-toolbar: Add add_to_size_groups()
  edfb1a2... application-main-window: Sync the pane size request
  12a7101... Use leaflets in the UI
  2139636... main-toolbar: Add add_to_swipe_groups()
  28e3192... application-main-window: Sync the leaflets' swipe state
  115b055... main-window: Add leaflet navigation with Alt+Arrow keys
  28a1977... main-toolbar: Add back buttons for leaflet navigation
  49823ec... application-main-window: add navigation via signle click on
  d97d86c... toolbar header group
  1f2896e... composer: Switch leaflet to composer when folded
  0b743ab... conversation-list: use shift+activate to open conversation 
  d6c546e... composer: close the composer when navigating back
  f8f223d... main-window: Block forward navigation when viewer is empty
  98017cf... main-toolbar: Create object containing conversation actions
  70a4089... action-bar: Add an action bar to the conversations list (2-
  d0fff26... Merge branch 'adaptive' into 'mainline'