This renames the "mock" code to "reference" because that's really what
it is. Also, some code has been moved from the CDM repo to a common
utility directory so that it can be included here, and the oemcrypto
unit tests can now be built without having access to a current CDM
repo.
There are no functionality changes in this CL.
This change updates the copyright notice to make it more clear that
the code is distribued under the Widevine Master License Agreement.
It also updates the unit tests and sample code to correct the useage
of AES 256. AES 256 is used to decrypt entitled content keys, but it
is not used to decrypt key control blocks.
