upgraded to hadoop 2.1.0 and replaced incompatible API calls.

replaced some lower level operations with the new NMClient.
Weave API changed to deprecate the setUser method
for the WeavePreparer since in hadoop 2.1.0 the user is not set
when requesting for a container, and instead the user submitting
the application is automatically used.

We will need to maintain 2 branches for a while to maintain compatibility with different version of hadoop.