Argument parsing and checking - allow token authentication

This expands the argument parser and ensure_auth_info method to
provide alternative means of authentication. Up to now the CLI
required username, password, tenant and Keystone URL. Now user can
also provide auth token and Tuskar URL (alternatively Keystone URL
instead of Tuskar URL, in that case the Tuskar URL would be fetched
from Keystone).
Set default service type to 'management'

We don't know yet what service type will be used in Keystone to
identify Tuskar service, but it sure won't be 'metering'. We should
rather get an unknown service type error than fetch a Ceilometer
service URL mistakenly.
Merge pull request #16 from jistr/ftr/auth_options

Allow token authentication CLI args