Cache drivers

Khulan - Kirby MongoDB Khulan is a cache driver and content cache with NoSQL interface for Kirby using MongoDB. K4
```
return [
  'cache' => [
    'pages' => [
      'active' => true,
      'type'   => 'static'
    ]
  ]
];
```
Staticache Staticache gives you the performance of a static site generator for your regular Kirby installations. K4 K3
PHP Cache Driver PHP based Cache-Driver K4 K3
Redis Cache Driver Redis based Cache-Driver K4 K3
SQLite Cache Driver SQLite based Cache-Driver K4 K3
MySQL Cache Driver MySQL based Cache-Driver K4 K3