[sugar] duplicate favorites

[Mikus Grinbergs]

Running Joyride, manually updated to 2056 level.  Happened to look 
at .sugar/default/favorite_activities.  Found many duplicates.

Most duplicate entries were for the same Activity, but at different 
versions.  However, some of the duplicate entries were for the same 
Activity at the same version.

Shouldn't whatever adds entries to favorite_activities be *deleting* 
previous entries for that same Activity ?

mikus