Use werkzeug to run the developement API server

https://review.openstack.org/154382
commit 09a2f0994fd284412e57fd42ac91ae980f166d11
Author: Mehdi Abaakouk <email address hidden>
Date: Tue Feb 10 09:41:05 2015 +0100

    Use werkzeug to run the developement API server

    wsgi.simple_server in a mono threaded process that can handle only
    5 requests at a time.

    Even the doc recommands to setup Ceilometer through an other WSGI services
    like Apache 'mod_wsgi', we can provide a better testing API server.

    So this patch changes the default HTTP server to the werkzeug one with
    a autodiscovery of number of workers that we can use.

    The client queue of werkzeug is 128, so on a 4 cpus machine, ceilometer-api
    can now handle 512 connections instead of 5.

    Also the change adds references of how to deploy pecan application in
    the documentation.

    The config option enable_reverse_dns_lookup can be safely removed,
    because werkzeug doesn't do any reverse dns lookup.

    DocImpact: configuration options changed:
    enable_reverse_dns_lookup removed, api_workers added

    Change-Id: If7450b393ea88bc185e5c82b706ace9c38ce350e