Collection count isn't properly updated after a rescan [0.3]

[Dan O'Reilly]

After a rescan, the collection count displayed in the lower right of the GUI isn't updated. This is because xlgui/main.py keeps a _cached_count, which is only updated if its current value is -1. So once its initially set when exaile loads, it never gets updated again. It looks like the collection.get_count() method used to update the cached length is just calling len() on the collection list (dict?), so I don't think there's any harm in just calling that every time we want to update the count in the GUI.

[reacocard (reacocard)]

Fixed in r1697