[ Merge of http://go/wvgerrit/100905 and http://go/ag/10708438 ]
Add support for ATSC certificate and licenses handling. ATSC
files are distinguished from the apps DRM certificate and licenses
by file naming conventions.
Bug: 139730600
Test: WV unit/integration test, GtsMediaTestCases
Change-Id: I295f66f92fe01d7716978deac9dc360d74addedd