Week 10: Making filters apply consistently

With the previous way of passing filters settings from DlgSelector to SelectorLibraryTableModel, a filter update and select() was executed for every change whether user-initiated or programmatic. Since the default behavior is to load filter settings programmatically when the seed track changes, and each control triggered the update, there were a number of redundant calls to select().

In order to fix this, I changed the API for SelectorLibraryTableModel: now, each filter has a corresponding "SelectorLibraryTableModel::setXfilter" function that changes the appropriate variable but does not trigger the filter update. Thus, SelectorLibraryTableModel::applyFilters must be called manually once all changes have been applied -- the "DlgSelector::filterByX" functions each call applyFilters, as they are meant to be connected to the appropriate signals from the UI, whereas loadStoredFilterSettings does so only once after all the filters have been changed.

This change fixes the issue where filters were not getting applied after the first track was played without manually checking/unchecking them, and cuts down on unnecessary database queries.

There is still an issue wherein, once a track has played, it always appears in the filtered set whether or not it matches the filters. Since I drop the temporary table (that stores the preview and score columns) whenever a new seed track is set, I'm not sure how or why the old track is being kept; this requires more investigation.