blueprint cisco-single-config

Scope: Unification of all the various plugin files for the Cisco plugin into a single file.

Use Cases: Quantum with the Cisco plugin.

Implementation Overview: All the config values contained in the various files in
etc/quantum/plugins/cisco will be unified into a single file
etc/quantum/plugins/cisco/cisco_plugin.ini. The plugins needs to be modified to
read from a single file instead of multiple.
Added quantum.openstack.common.cfg support.

Change-Id: I9ef356eccfe330c3733f441b96400d03c3d7d1df