Fix indentation for 'Move class to File' function

'Move class to File' function did always use tab as indentation
character. As space user you always had to convert the tabs to spaces by
hand afterwards. This fix tries to find and set the right indentation
character. If no indentation character is found, it falls back to tab.
Merge pull request #366 from sven-n/fix-move-class

Fix indentation for 'Move class to File' function
Update string resources.
Fix #311 - AvalonEdit cannot be used in WPF application with multiple UI threads.
Handle errors when saving the code completion usage cache.
StorageLocationPicker: fix switching from a configuration-specific location to the base location.

The CoerceValue-callback is not called by WPF for values set by the control itself, so it was setting ProjectProperty.Location to PropertyStorageLocations.Unchanged instead of PropertyStorageLocations.Base.
Merge remote-tracking branch 'origin/4.x' into master.