supporting -exec, make it simpler
Merge pull request #1780 from feinstaub/topic_minor_GUI_fixes

minor GUI fixes
Obtain candidate list in main thread to avoid cross thread access to gui component. Closes #1783.
Return all items.
ConfigFile.GetConfigSections() transformed to property
Heads renamed to Refs when appropriate
Merge remote-tracking branch 'gitextensions/master' into topic_pushtoremote

Conflicts:
	GitUI/UserControls/RevisionGrid.cs
fix merge errors