LMP: added 'clear line edit' action to ArtistBrowserTab.
Merge branch 'master' of github.com:0xd34df00d/leechcraft
Aggregator: 100x Core::GetCategories() speedup.
Aggregator: don't request items twice on channel changes.
Util: check all cats in CategorySelector by default.
Aggregator: don't select all categories.

SetPossibleSelections() does this now, so we gain around 1/3 speedup.