Work/git status visual imp

This revision includes:

• Show only filename in status tree view to make it usable. Paths are long and never fit
• Add tooltips to file items. Tooltips show path + status text
• Fixed crashes when viewing raw diffs
• Added a refresh button to toolview
• Status view now has two columns, one to show the status and one for file names
• Ask for confirmation before removal / discard
• Open file (allows using gitwidget as a quick file explorer)
• Discard and Removal for a selection of files