Setting tag PLCAPI-4.3-23

Setting tag PLCAPI-4.3-23
Ongoing work to add upcalls, using new SFA class
new methods BindObjectToPeer, UnBindObjectFromPeer, still for SFA
reviewed type-checking for the 3 taggable classes node-interface-slice
cleanup ald dummynet stuff
expose the 'extensions' accessors to the API
tweaked checks in AddSliceTag
GetPersons exposes roles by default
bugfix in ReportRunLevel for non-string levels
tweaks in GetSlivers ( seems that it now exposes the keys for the root context )