MahApps 2.0 and friends

Changes:
-Added virtualization to the thumbnail list. This should improve performance and avoid using excessive amount of CPU and memory to try and load all thumbnails at once.
Because of this the thumbnail box will be limited to a single column. Max thumbnail size increased to 240 due to this.
-Window title is now case-sensitive.

Updated:
-MahApps to 2.0.1. Significant visual and behind the scenes changes.
-Libraries.

Fixed:
-Crash when deleting an image if its the last one viewed.
-Settings 'connection line' not changing accent if its on and user changes app accent colors.

Optimizations:
-Overall performance should be improved.
-UI.
-Startup speed.
-GIF tag on thumbnails render position.