Move from arbitrary resource filters to fix ones

Move from arbitrary resource filters to fix ones

Resource filters are used when generating additional APK containing only
specific resources.
The previous UI allowed for any type of filters, but we are moving to a
simpler way with fixed filters.
The first one is the density. Selecting the filter will generate 4 APKs per
application: default (all resources), hdpi (only hdpi/nodpi and default
resources), mdpi, ldpi.