Added an update_resource() function; works exactly like import_resource() (and
in fact the latter now simply calls the former after having created the
resource), but works on existing resources.

This lets you update files without having to replace them (and lose the original
resource ID, and fields in the process).


git-svn-id: http://svn.montala.net/svn/resourcespace@4233 c08608d7-6e46-0410-86ca-f2a6f1370df5