Add cluster-template-create to CLI

cluster-template-create takes a json data structure and passes it on
to the Savanna API. The data structure is read from stdin by default
or from a file provided by the --json parameter.

Change-Id: Ia824eb54b1f255ead8ea1a3e9cdff9ad8bdb07a9
Implements: blueprint python-savannaclient-cli
Add cluster-create to CLI

cluster-create takes a json data structure and passes it on to the
Savanna API. The data structure is read from stdin by default or from
a file provided by the --json parameter.

Implements: blueprint python-savannaclient-cli

Change-Id: I08cd3a38df81e78c71cfbc7cdb4bd59902b2d374