Add a HTML cache system

[jlambe]

For developers using the themosis/themosis stack, setup a file cache system for WordPress.

The first iteration for this cache will be by using files but it has to be flexible enough to add other solutions like Redis, ...

I invite developers who have experience with caching in WordPress or other solutions to share their ideas or issues they met.

[bactisme]

I confirm, that would be f**king useful to have new scout functions to cache some part or scout template

[jlambe]

Explore illuminate/cache APis and add WordPress cache drivers.

[jlambe]

Release 2.1 is supporting the installation/desinstallation of WordPress drop-ins. The master branch already contains a default object cache drop-in for WordPress that leverage the stack default configured cache solution (file, database, redis, memcached, ...).

Providing a HTML cache system means developping an advanced-cache.php WordPress drop-in so the returned response can be the cached HTML before doing a full round into WordPress. I can see what dedicated plugins face on this like handling content update, comments updates, ...

We need to list elements that need attention in order to purge the cache automatically as well as providing CLI commands to manage this.