Code review comment for lp://qastaging/~azzar1/unity/filters-fixes

Too many mistakes :/

> Did you make sure this doesn't change the way the dbus signals are sent to
> lenses? (from looking at the changes it shouldn't though)

There's a TestRatingsFilter (or something like that) and it's ok after the changes.

The changes to UnityCore/RatingsFilter.cpp make sure that after calling ::Clear the ratings property is really setted to 0 (how happens with the other filters). And the canges make sure that setting the ratings property to 0 (or calling ::Clear) the filtering property is "setted" (quotation marks because it'a read only property) to false.