support console APIs for nimble instance

Gerrit topic: https://review.openstack.org/#q,topic:bp/support-console-p1,n,z

Addressed by: https://review.openstack.org/442345
    Add function to get the console info from ironic

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

Addressed by: https://review.openstack.org/445283
    Add consoleauth manager

Gerrit topic: https://review.openstack.org/#q,topic:bp/console-support-p4,n,z

Addressed by: https://review.openstack.org/445324
    Add service entry for shellinabox console proxy

Addressed by: https://review.openstack.org/445321
    Add engine api for getting console info

Addressed by: https://review.openstack.org/445286
    Add service entry for consoleauth service

Addressed by: https://review.openstack.org/445323
    Add shellinabox console handler

Addressed by: https://review.openstack.org/445322
    Expose the API of getting console info

Addressed by: https://review.openstack.org/445285
    Add rpc api for consoleauth manager

Addressed by: https://review.openstack.org/445434
    Add desription of enabling console in quick-start doc