Updates issue #85 : Improvements to file handling
Display error information if file loading fails
Continue loading XML file after errors - TODO need to report these errors still
Save As always enforces .GRF extension (e.g. if saving graph created from rendering media file)
Drag and drop and recent file selection of media files adds media file to graph rather than rendering to new graph
File opening paths bottle necked in TryOpenFile and duplicated set up code combined
Use default file name base for saving screen shot file
Add file name caption to progress view
Display name of opened XML and media files in title bar
Some obsolete and unnecessary code removed


git-svn-id: http://graph-studio-next.googlecode.com/svn/trunk@142 c2f33eb2-41b2-391d-4cb4-d9d0608729ba