Adding a method to the WeaveController which will return back the
resources used by the application, broken down by runnable name.
The application master starts a service for this purpose which
the controller can query and return back the report.
cleanup of comments
Fixes from pull request.

Added javadocs where they were missing and more details where
it was lacking.  Tracker server binds on a random port by
itself instead of on the port passed into its constructor.
Some code style fixes.  Deprecated getCores and setCores for
a ResourceSpecification in favor of getVirtualCores and
setVirtualCores since they more accurately reflect reality.
Merge pull request #43 from continuuity/feature/expose-resource-usage

Feature/expose resource usage