Switch to oslo.config

The config module in oslo-incubator has been replaced by oslo.config.
Projects need to switch completely to oslo.config for kilo.

This patch does:
* Register options with oslo.config (new file manila/opts.py)
* Generate the config file using oslo-config-generator
* Remove obsoleted entries for this from openstack-common.conf
* Remove oslo-incubator config files

Change-Id: I30b594423c08782e13a1f615099ae65f997a8551
Closes-Bug: #1382183
Merge "Switch to oslo.config"