Autohide toolbar on scroll

[nvllz]

This PR aims to improve reading experience as well as add a modern touch while not breaking a thing.

4475-4232-b535-b1ac95779ce.mp4

• replaced actionbar with toolbar on article screen and made it collapse/show on scroll
• preserving current fullscreen mode state (hide article toolbar)
• collapse the mainactivity toolbar on scroll and automatically show it with onResume
• improved status bar coloring consistency – match toolbar (primarycolor) to make the collapsed state more appealing
• tested with all themes, as I didn't want to break anything
• fixed some deprecated values (sp, fill_parent)

Closes #1215 #114 #442