Bug 12068 - Auto reload documents from VCS changes.

This patch adds a new property to FileEventArgs to know if it's a VCS change,
which is then used to trigger a reload and never ask user for info.

It's safe, since changes are stashed then reapplied or the user is told about
possible loss of changes.
Renamed property from IsVersionControlChange to AutoReload.
Refactor code to use extra methods and not optional parameters.

Fixed a case where file unsaved changes would be lost.
Merge pull request #327 from mono/autoReloadVCS

Bug 12068 - Auto reload documents from VCS changes.