Merge pull request #70 from ehmatthes/optimize_queries

Optimize queries
Merge pull request #71 from ehmatthes/optimize_queries

Optimize queries
Merge pull request #72 from ehmatthes/optimize_queries

Optimize queries
Merge pull request #73 from ehmatthes/optimize_queries

Optimize queries
Slight change to load testing data generation.
Factored out creation of submission set from index, new, and now more_submissions pages.
Link to a more_submissions page.
Index, more_submissions pages only show more if there are actually more submissions to show.
Submission numbering is correct on more_submissions pages.
Made page more_new_submissions.
Merge pull request #74 from ehmatthes/ongoing_development

Ongoing development
Removed most view-caching code, left in calls to invalidate.
Added simple queryset cache to index page.
Removed caching of querysets; subtle effects such as more_submissions becoming stale.
Added prefetch_related('submitter') to users with show_invisible=True.