Switch to sphinxcontrib-pecanwsme for API docs

Move the ceilext code into a separate package
so it can be worked on and reused by other
projects using Pecan and WSME.

The new package is being added to the requirements
list under https://review.openstack.org/29149.

Change-Id: If38a69ed8ef654e75bb29da998fbb731143c506c
Signed-off-by: Doug Hellmann <doug.hellmann@dreamhost.com>
Merge "Switch to sphinxcontrib-pecanwsme for API docs"