NodeConditions (trying new approach)

Doing major changes in conditions, to make them more abstract and
capable of handling more complicated constraints. The idea is to
propagate new conditions along with new mappings through the algorithm.
It's for now restricted to the node matching algorithm, but I might apply
the same idea to edges.
Now we have a danglingCondGen and a delCondGen

Names might change, but in essence we have now a matching algorithm
that handles two cases:
	- delCondGen: avoids a node marked to be deleted to be mapped
		to another one.
	- danglingCondGen: avoids a node with an edge pointing from/to it
		to be deleted.
removed old node mappings funcs