DoubleTap-Action preference for the advanced settings

Added a "double-tap action" setting to the advanced settings.
Values for this setting are "Show Original Artwork"(default) and "Next Artwork".

I had to mess with forward referencing views in the RelativeLayout in the SettingsAdvancedFragment so that "DIM" and "BLUR" get as wide as "D-TAP". Perhaps another layout (Table) would make sense there?