[ADD] oe web: run an OpenERP web process.
[IMP] oe web: option to use gevent WSGI server.
[ADD] oe: added cron sub-command to run a single process dedicated to cron jobs.
[IMP] oe cron: use setproctitle, set openerp.multi_process.
[IMP] oe web/cron: slight refactor.
[FIX] oe web: always set gevent in tools.config.
[DOC] added prose for oe web and oe cron.
[IMP] oe web: use openerp/__init__ instead of tools.config to store the gevent flag (similarly to the multi_procsess flag).
[IMP] oe web: handle SIGINT and somewhat SIGTERM for the gevent case.
[IMP] oe read: use the environment if --addons is not provided.
[IMP] oe read: use common.set_addons().
[MERGE] merged oe-related changes:

- added a cron command
- added a web command
- added rst documentation
- changed the read command to use the environment when --addons is not given
[DOC] updated gunicorn doc, a.k.a. why we can't have nice things.
[IMP] oe initialize: added --coverage flag.