middleware file that contains handling for database OperationalErrors and throws up error pages when a user tries to navigate away from their current webpage if celery, solr, or galaxy is unavailable
Added a field for the number of seconds between each time the periodic tasks poll for the status of the external tools
Added in more explicit error handling and some extra code to make use of the new model field.
Base template for Database, Celery, Solr, and Galaxy 500 errors.
added middleware classes
Merge branch 'develop' of github.com:parklab/refinery-platform into develop