Configure nginx to run properly under supervisord

Don't daemonize. Use exec in startup script.
Get postgres working properly with supervisord.

supervisord fails to shutdown postgres cleanly when it's run using
`su omero -c "$PGBIN/postgres -c config_file=$PGCONF"`
because su starts another shell which means the QUIT signal doesn't get passed to postgres. E.g.

2014-08-11 15:11:06,560 INFO waiting for pgsql to die
2014-08-11 15:11:08,563 WARN killing 'pgsql' (133) with SIGKILL
2014-08-11 15:11:08,563 INFO stopped: pgsql (terminated by SIGKILL)

Note `su omero -c "exec ..." doesn't work either. The user to run postgres is now set in supervisord.conf, but to allow auto-creation of the database data dir (which must be run as root) a one-time setup script has been added.
Split omero supervisord startup into root and non-root commands.

As with postgres use the supervisord user switching capability instead of `su -c`.
Fix wait_on_postgresql to use the correct data dir
Incorrect branch, OMERO-5.0-latest-build should be OMERO-5.0-latest
Run web using the omero user in supervisord
Tidy up priorities (leave space for other extensions)
Forgot to add new files to Dockerfile
Include /etc/supervisor/conf.d/*.conf

This makes it easier for other containers to extend this one.
Add "$@" to /supervisord

Useful for testing, e.g. you can start the container and pass "-e debug" to get debug logs
Add pytables to omero-base
Use default TERM instead of QUIT signal

QUIT causes omero and web to core-dump.
Add basic argument checking to graph.py
Optionally use a custom :tag that isn't in the folder name
Replace felix/openjdk with ubuntu:12.04, install openjdk-7-jre-headless
Remove dpkg-divert initctl

Fixed in the current ubuntu:12.04 image:
$ docker run -it ubuntu:12.04 ls -l /sbin/initctl
lrwxrwxrwx 1 root root 9 Apr 25 02:43 /sbin/initctl -> /bin/true
Use official centos:centos6 instead
Add a centos 6 image for building OMERO in multiple environments

Ice 3.3, 3.4, 3.5
Java 1.6, 1.7
Python 2.6, 2.7 (2.7 with Ice still needs to be sorted out)
Merge pull request #9 from manics/omero-build-c6-multienv

Centos 6 image for building OMERO in multiple environments
Remove python27 path if python26 requested

Closes https://github.com/omedocker/omedocker/issues/10