Exceptions Handlers, Test Updates, Tokens

* Implements encryption/decryption for api tokens - secret key set in jumpgate.conf- Resolves #21
 * Also adds expiration date check and correct tenant_id check
* Implements Validate Token Endpoint - Resolves #22
* Adjusts tempest tests to be up-to-date with tempest master (lots of renames and some removed tests)
* Uses Falcon's New Exception Handler