not using RTYPE in filter
simplify import
adapt mapply
rework pmin and pmax on top of mapply
added is_mapply_compatible trait class
added same_mapply_scalar_type
using mapply_scalar_type
reimpl pow using mapply
rework rep and rep_each
rework rep_len
rework replicate
simplify sapply
rework rev
replaced sugar::Range by sugar::Seq
sign uses sapply
simplify transform. closes #192
rm Arith_Vector_Vector -> this is a special case of mapply
impl Arith_* with mapply
unary impl using sapply
impl Comparator using mapply