log more of the errors during discovery, including when a GAV is not found. Be sure to close the graph workspace after resolving repository contents. Don't require source URI and GAV in order to log an error (which might be a mistake down the road...though this means making the same assumption about GAV immutability as maven itself).

TODO: Resolve API differences from patched sources. That's in the next commit.

Conflicts:
	src/main/java/org/commonjava/maven/cartographer/data/CartoDataManager.java
	src/main/java/org/commonjava/maven/cartographer/data/DefaultCartoDataManager.java
	src/main/java/org/commonjava/maven/cartographer/ops/ResolveOps.java
fixing merge problem in ResolveOps, and also fixing graph-cleanup logic a bit.
correcting api incompatibility stemming from merge