Redis View Counters - Xenforo 2 2.4.0

Moves some view counters to use Redis-based increment counters rather than scratch tables in MySQL. Redis provides atomic get & del when pushing view counts totals into the database.

Note:

• Currently only handles thread or attachment views.
• There is an effective limit of ~100000 threads that can be updated per 'Update View Counters' cron task run.