Reviewer Mike - Sproutlets control record routes

Mike, this implements the long-discussed changes to the Sproutlet API to allow Sproutlets (but not ASs) to more accurately control the Record-Route sets.

I've tested by running the existing UTs (not your new ones yet) and the only outstanding issue is that the SCSCF Sproutlet sometimes adds itself to the route set multiple times in a single hop.  This breaks two SCSCFTest test.
Doesn't look like we use this method anywhere anymore, and it is probably dangerous to leave it here - the Sproutlet's shouldn't care whether a URI is local (ie. local to the SproutletProxy) only if it refers to the Sproutlet itself (is reflexive in current terminology).