Bug 512 - Autosave open files when committing.

I've added a dialog for asking the user what to do with unsaved files.

In case we have open documents, ask the user if he wants to cancel the commit
operation, save the files or ignore local changes.
Fixed up messages and case where files wouldn't get saved.
Merge pull request #328 from mono/autoSave

Bug 512 - Autosave open files when committing.