User online status caching (#94) * WIP on cron + Redis caching of connected users per locale * Language support tweaks * WIP on more logical locale support; fav users filtered by locale * WIP on Redis caching of presence using sets; moved type definitions * WIP on Redis caching of user presence data * WIP on online user caching * WIP but code is now consistent; needs test * Cleanup of unused variables in firebase.py * Added user parameter to render_template() calls; code formatting in cache.py * Bug fixes in Redis online status handling code * Added online user update job to cron.yaml * Added TTL caching of online users * Add attribution & copyright for Norwegian word frequency data * Reduced in-memory caching of online users to 30 seconds * Skip user online query if robots only * Removed unused class