Expanded view

Fixes #41 and also:
*Added InverseBooleanToVisibilityConverter.
*Some tabs to whitespace in an unittest file.
*Fixed a few typos.

Phil, please check the way I did the property stuff and tell me if there's an optimal way than that Expanded manual setting in Expanded/Collapsed functions.

Also, permission to add options to modify these behaviours? As in:
Option1: Setting Adorner visibility to Always Visible/Always Hidden/Based on Expanded
Option2: Setting Description in Expander to Visible/Hidden.
Option3: Setting SHA title to short/long SHA

Will be done through a cogwheel icon which makes a dropdown menu.