Memcache for users and competitions

Introduced memcache feature for accessing individual users and
competitions, and all competitions.

Part of issue #16
Memcache for users and competitions - extras

Missed some user and competition memcache changeds.

For issue #16
Modify competition page

changed position of error message so it doesn't overlap with competition
description.
Memcache competiton create csv results

Add memcache get competiton

For issue #16
Memcache: photo handlers

Add memcache wrapper for getting individual photos, user photo list,
competition photo list, and deleting stale cached items for the lists
when a new photo is added to the database.
Modify get_user()

It now returns both user_id and user object.
Caching pages

Cache user pages and the competitions page for all users and for the
case when no user is logged in.

For issue #16
Merge branch 'memcache'