Summary:
This is #2 of a series of changes. It did the following:
(1) a few refactor of the MKL memory interface
(2) an initial MKLContext to deal with MKL specific computations
(3) Provide MKLMemory access in Python with the blob feeder/fetcher registration.
Reviewed By: dzhulgakov
Differential Revision: D4210123
fbshipit-source-id: adea1f1ffbd0b9ffdd55092676468c16bec08992