Fix caching

[zonky2]

Currently caching doesn't works - see error

PHP Warning: Failed to save key "c86023c00f02b24d09af39d643969cd4" of type ContaoCommunityAlliance\DcGeneral\DcGeneral: Serialization of 'Closure' is not allowed in /project/vendor/symfony/cache/CacheItem.php on line 161

[discordier]

Note to self:

The DcGeneral Factory must be reverted to use an ArrayCache for instances of DcGeneral but must use the configured stored cache to cache the instance of the Definition container instead (which should be serializable).