Removed unused context-related method for ONE

Decoding Base64-encoded context is no longer necessary.
Minor dep update
Deep-freezing user structures to prevent modif.

Deep-freezing user structures in authentication strategies
prevents later modification, intentional or unintentional.
Minor version bump to 1.0.0.beta.5

Changes:
* Basic controller specs added
* Fixed DummyBackend fixture loading
* Updated deps (minor updates)
* Cleaned-up contextualization behavior for the OpenNebula
  backend (USER_DATA in Base64 only, no tricks for Cloud-Init)
* Aligned DummyBacked behavior (raising errors instead of returning
  false on critical events)