OC-7: Reorganize build

This fixes the sample plugin versioning, and also reorganizes the ocelot build so everything (app + plugins) will build from the top level.  The app and the sample plugins are set up as submodules.

The bad news is that to make this work, the top-level pom.xml needs to be package type pom (instead of jar), so the ocelot code itself needs to be dropped down to a subdirectory.  So there's a lot of renames.  (Use `git log --follow` to show history across the move.)  On the other hand, maybe better to do this now while the project is still pretty young.  

You can still build just the ocelot app by building from within the `ocelot/` subdirectory.

You may want to pull this branch locally and look at how things work now before you merge it (assuming you think this is a good idea at all).