Refactor / cleanups

Some general thoughts I've jotted down while going through the code. Writing them here to start tracking progress for them.

1. Refactor giraph.graph to giraph.master, giraph.worker. The whole giraph.graph package name is bad in general I think.
2. Cleanup giraph.utils. For example move timers stuff to giraph.time.
3. Change module names to be more maven-esque, that is something like giraph-root, giraph-core, giraph-formats.
4. Remove WorkerClientServer. Is this needed anymore?
5. Cleanup MasterThread#run: long convoluted method.
6. Cleanup BspService#process: lots of duplication. Use a vector of events or something.
7. Cleanup Vertex class: seems to me it has too many methods and should be a simpler interface (maybe even eventually an actual interface! not an abstract class). Add something like a Vertexes/Vertices class with helper methods that use can use.
8.

Observer. Discussed elsewhere already. ALlow users to easily plug in code at various points in the system. Essentially a cleaner implementation of e.g. WorkerContext
9. Cleanup GraphMapper. I don't see why we even call a map() method seeing as we are overriding run(). We are clearly not particularly "mapreduce-y" so we should make it our entry point more clear than a map(). Also I think we should have something like a WorkerThread similar to MasterThread and clean up all of this to just creare whichever threads the node is assigned roles of.
10. Move examples and anything else not needed for a giraph library out into it's own package (like giraph-examples)?

If someone +1s the ideas I'll work up some patches. Feel free to add other cleanup things here as well.