[Enhancement] Show more Redis information on /setup page

[exodus4d]

With the next release v1.5.0, a number of changes are made to caching in Pathfinder.

Best practice:

The default filesystem based cache, can already be replaced by Redis (see wiki:cache).
PHP´s default filesystem Session handler, can be replaced by Redis as well. Which is much more performant than Pathfinder`s default mysql Session storage. (see Set Up a Redis Server as a Session Handler for PHP)

What is new?

In v1.5.0 the exodus4d/pathfinder_esi client can handle its own cache backend where ESI responses get cached by their Expire HTTP header information.
If Redis is already configured as Cache backend for Pathfinder, it will be shared with ESI client.
A better solution is a distinct Redis DB for each use case. This gives you more control over caches. - e.g. Cached ESI requests can be cleared, Pathfinder cache data is not.

To keep track of the Redis instances (and databases), /setup page now shows detailed stats from all Redis caches that are used.

Examples:

1. ❕ No Redis cache configured (default) - [filesystem cache]

2. ✔️ One Redis instance (port 6379), with distinct databases

3. ❕ One Redis instance (port 6379), with shared db0 for "PHP Session" + "API_CACHE" data. This works but is not recommended!

4. ✔️ Three Redis instances (port 6379, 6380, 6381), with distinct databases

[hilocz]

Exodus in text there is version 1.5.0 , but milestone is 1.4.4 .

[exodus4d]

@dkrotil thanks! I´ll rename the milestone. The next release will be v1.5.0.

• The new PHP v7.1 requirement (current v7.0) is the reason for it.

[exodus4d]

More changes:

• Redis databases can now be flushed individually from /setup page:
  
• Cached TEMP files (e.g. compiled HTML templates) in dir (default: tmp/) can now be deleted from /setup page: