Parsing basic map
Implement length($map)
Implement map-get($map, $key)
Implement map-has-key($map, $key)
Implement map-keys()
Implement map-values()
Implement map-merge($map1, $map2)
Implement map-remove($map, $key)

This only implements the 3.3 syntax.
Implement keywords()
Merge remote-tracking branch 'xzyfer/feat/maps'