properly handle required/optional args

[fixes #330]
Merge pull request #333 from hartzler/python-admin-args-fixup

properly handle required/optional args
Should stop the trace when it stalls because of NodeStore breaking a path.
split NodeStore into public/private structures
Removed some new-pathfinder stuff which didn't work out.
Split out NodeStore administrative functions to NodeStore_admin and paid down technical debt with proliferation of #include NodeStore_pvt
Merge branch 'master' into improve-nodestore

Conflicts:
	dht/dhtcore/NodeStore.c
	dht/dhtcore/NodeStore_admin.c
	dht/dhtcore/NodeStore_admin.h
	dht/dhtcore/NodeStore_pvt.h

This was due to my poor communication :)