CLI for Capabilities Web API

We can have such command after this blueprint has been implemented:

    zqfan:python-ceilometerclient$ ceilometer capability-show
    +---------------+---------------------------------------------------------+
    | Property | Value |
    +---------------+---------------------------------------------------------+
    | alarm_storage | "storage:production_ready": true |
    | api | "alarms:history:query:complex": true, |
    | | "alarms:history:query:simple": true, |
    | | "alarms:query:complex": true, |
    | | "alarms:query:simple": true, |
    | | "events:query:simple": true, |
    | | "meters:pagination": false, |
    | | "meters:query:complex": false, |
    | | "meters:query:metadata": true, |
    | | "meters:query:simple": true, |
    | | "resources:pagination": false, |
    | | "resources:query:complex": false, |
    | | "resources:query:metadata": true, |
    | | "resources:query:simple": true, |
    | | "samples:groupby": true, |
    | | "samples:pagination": true, |
    | | "samples:query:complex": true, |
    | | "samples:query:metadata": true, |
    | | "samples:query:simple": true, |
    | | "statistics:aggregation:selectable:avg": true, |
    | | "statistics:aggregation:selectable:cardinality": true, |
    | | "statistics:aggregation:selectable:count": true, |
    | | "statistics:aggregation:selectable:max": true, |
    | | "statistics:aggregation:selectable:min": true, |
    | | "statistics:aggregation:selectable:stddev": true, |
    | | "statistics:aggregation:selectable:sum": true, |
    | | "statistics:aggregation:standard": true, |
    | | "statistics:groupby": true, |
    | | "statistics:pagination": false, |
    | | "statistics:query:complex": false, |
    | | "statistics:query:metadata": true, |
    | | "statistics:query:simple": true |
    | event_storage | "storage:production_ready": true |
    | storage | "storage:production_ready": true |
    +---------------+---------------------------------------------------------+

Gerrit topic: https://review.openstack.org/#q,topic:bp/capability-cli,n,z

Addressed by: https://review.openstack.org/133324
    WIP