finished Transient.Map as a drop-in replacement for java.util.HashMap

[jurgenvinju]

• implements java.util.Map{put,putAll,remove,removeAll} by forwarding to Map.{__put,__putAll,__remove,__removeAll} instead of throwing UnsupportedOperationException
• added some @SuppressWarnings
• this allows me to use Transient.Map.of() instead of new HashMap and save quite a bit of memory in Rascal's interpreter.

[jurgenvinju]

@msteindorfer do you see anything against this? I'm now using __putAll in an experiment and that seems to work fine as a replacement for putAll. Of course for the Immutable versions this does not make sense; but I'm interested in using our Transient versions.