Blender Git Loki

Make Toolbar Tabs more readable

This makes the tabs slightly larger, increases the text size slightly, and adjusts the colors a bit to improve overall contrast. It also makes inactive tabs draw with a full tab shape, improving the readability at a glance, particularly when tabs are very small.

The users most affected will be those on smaller displays, where previously tabs were very difficult to read.

Reviewers: @billrey, @campbellbarton

Differential Revision: https://developer.blender.org/D170