This change relocates the mistral resources from the contrib area into the main
resource tree. It was originally added to contrib/ because of the project's
incubation status, and more specifically because the client is not in the
global-requirements.txt file. However, when this was discussed at the summit in
Vancouver, the decision was to move the resources to main tree but skip
registration if the client is not installed. This will save users from the
trouble of installing it as a plugin.
Change-Id: I6eeef5fa2b080df610e52620d2b935450d8d49e3
c31a9533fa