[MERGE] wsgi overhaul, native arbiter, service and startup cleanups

add a generic wsgi entry point openrp-wsgi.py that should work for all wsgi servers (gunicorn, uwsgi, ...)
add a simple native multiprocessing arbiter option --workers=num
add limits options (cpu, memory, time) for the native aribter --limit-*

bzr revid: al@openerp.com-20120922114750-obpf7ydtupem9ke9