Revise map handling

[blackwinter]

Investigate whether to unify put_*map() into put_map() with map type determined by file extension or explicit type parameter (and allow implicit lookup() with the same logic) or migrate put_*map() (and lookup() with named maps) to Catmandu's store concept (see also lookup_in_store()).

Originally posted by @blackwinter in metafacture/metafacture-fix#229 (comment)