Move private functions of NodeStore to node-store-private.h
Fix slip of the pen in overlap test
Move node_hash and node_equal to node.c
Force destroy canvas wire on vulcanize, add wire_item dispose func, add arrows to wires in debug mode
Merge branch 'vulcanize-wires-impl' into HEAD

Conflicts:
	src/model/node-store-private.h
	src/model/node-store.c
Add T-crossing test, fix related issues
Fix a bug existing wires not showing

This caused quite some confusion when using complex circuits.