Updated files

Changed file dialog to NOT remove the name of the file in the file box when switching directories.

Began work on deferred texture loading for sprites.
Updating sprite editor plug-in

Corrected issue with import of v1 sprites and texture sizes.
Added sprite editor plug-in functionality.
Added ability to re-load content in editor.
Added ability for content plug-ins to check for existing plug-in dependencies (including plug-ins that implement IImageEditorPlugIn).
General cleanup.
Updated example resources

Added fixed up sprites to the file system.