Switch celery keys to be all-uppercase

[Christopher Allan Webber]

Celery will finally be moving to a structure that will be much, much easier for combining with MediaGoblin. Horray!

http://ask.github.com/celery/internals/app-overview.html

In order to better prepare for this, we should switch our config system setup for celery's configuration to also have all celery-relevant keys to be ALL_UPPERCASE in form.

So a few changes:

• Update mediagoblin/config_spec.ini and set all keys to UPPERCASE form.
• Update mediagoblin/init/celery/init..py 's setup_celery_from_config and remove the force-to-upper... well maybe anyway! I suppose it doesn't hurt to include this, but it isn't necessary any more.

This is a simple, bitesized task, appropriate for a new contributor.