implement key in (list of values) filters

implements key in (list, of, values) selector. For example: highway in (primary, secondary, tertiary) and type:way.

todo / open points:

• implement parsing of its negation? key not in (list, of, values)
• implement negated list variant(??) key not (list, of, excluded, values) (would be equivalent to key=* and not key in (list, of, excluded, values)), could be useful for queries like building not ("no") //edit: maybe an alternative, more clear, syntax would be key = * excluding (list, of, excluded, values)
• unify with = selector, so one could just write key=(list,of,tags)?