Redis View Counters 2.2.0

• Add support for page view counts

• Require php7+
• Require XenForo 2.1+, drop XF2.0 support
• Correct how paging through redis results is done, to ensure all items are visited as expected. This only effects installs with very large number of redis keys in the one instance

• Minor code cleanup
• Improve extendability for ElasticSearch Essentials for pushing view counts into search

• Only warn if Redis Cache isn't configured, do not block installing/upgrading

• Fix that view counts may be attributed to the wrong thread

• Block installing if Redis Cache add-on is not installed & configured.

• v1.x.y is XF1, so bump to v2.x.y
• phpdocs + cleanup

• Depending on Redis Cache 1.1.0