Customized timeline tabs

[yvolk]

Give users an option to switch from standard Android's Action Bar to customized timeline tabs.

We had similar topic some years ago "Use tabs instead of buttons" #113. That time we removed buttons from the old fashioned (for that time :-) ) Action Bar and replaced them with controls on the Navigation Drawer. Action bar became an ordinary action bar: with a Title, Subtitle, Action buttons and the "overflow button" (three vertical dots), containing actions that didn't fit on the Action Bar.
Some Android apps (e.g. GMail app) still have this layout, but for easy switching between small number of main options (timelines) some apps add tabs below the Action Bar or even replace the Action bar with tabs completely.

1. I understand that timeline tabs cannot replace timeline selection from a list simply because AndStatus may have hundreds of timelines (see "Manage Timelines" in the menu), but for the simplest use cases we need to give alternatives to a User:
   1.1. An Action bar with a Title/Subtitle and action buttons or
   1.2. Timeline tabs or
   1.3. An Action bar + Timeline tabs below it.

2. In addition, we will add "Post" FAB (floating action button) as an option, to create a new note.

3. An Action bar / Tabs / FABs will be collapsible, i.e. they will be hidden when a timeline is scrolled down. This behaviour is provided out of the box by the Android Coordinator Layout ( see e.g. http://saulmm.github.io/mastering-coordinator )