rework UI - part 1

* switch to components from the support library
 * replace PagerSlidingTabStrip with TabLayout
 * switch to ToolBar in list view and details view
 * unify details view in phone and tablet layout
* add FloatingActionButton in task list
* change scroll animation of title in details view
* move delete option in details view to overflow menu
* improve tablet layout

Still to test: Android 2.x