* EncryptionKey now contains them rather than a PSSH box.
* Outputs PSSH boxes for each entry.
* Outputs a ContentProtection element for each entry.
* Removed SystemName and UUID from KeySource.
* Removed --scheme_id_uri packager argument.
Issue #88
Change-Id: I2651784c3220fd64f5b1773fdcd70285690cf8c0