Revert "Add support for allow-permission extension."

This is not currently in use and can be replaced by a better solution.

This reverts commit 33110a0b2f4cdfd2ee6911a479d1fbbcd14bc389.

Change-Id: I672381398c8d09275226a0ef4ead408e2ccbd040
Allow granting permissions based on signature in <allow-permission/>

This patch allows us to either specify a sharedUserId or a package
signature to use when granting the specific permission.

Change-Id: I8aed78d40316e0e94ac1bfefc7c4a3016a2a9a6b