* cloudscale_server: remove required parameter check
The valid parameter combinations are already checked by the API. There
is no need to check a subset of this in the Ansible module as well. This
makes it more likely that future changes in the API won't require
changes in the Ansible module.
* cloudscale_server: add password parameter
Recent revisions of the cloudscale.ch API allow setting a password for a
server. Add this option to the cloudscale_server module.
