Move out Security REST API

Security REST API moved out (into Nexus restlet1x plugin).
REST API, unlike other security components, were nowhere else used
than Nexus, and reason for it that they were implemented using
plexus resltet bridge, another nexus specific stuff.

By moving out these two modules (and merging them into nexus restlet1x
plugin) we make Security totally nexus independent.

The UI accessing these REST APIs were anyway left in Nexus UI,
when resources were moved out.