Add cache for service container

[dominikzogg]

Would be cool, it there something like a 'listener' stops autocomplete (or use cached infos) until the needed files in app/cache exists again.

[Haehnchen]

related #238

[Haehnchen]

rm -r app/cache => NullPointerException: null keys not supported: null keys not supported

[Haehnchen]

together with #350