Major refactor of ModelReflectionService to enable the use of the same ModelReflectionService for multiple Ember packages.
* metaModel array indices of ModelReflectionService is now prefixed with packageKey (eg. Mmitasch.Taskplaner)
* all methods of ModelReflectionService now additionally expect a packageKey

Removed dependency of ModelReflectionService from EpfSerializer => MetaModels of package are passed through constructor

Ember.yaml content is now prefixed with packageNamespace + packageName to enable config for multiple packages