[FEATURE] index creation with index settings for aliases

The name of the index could be given now by other Packages like Flowpack.ElasticSearch.ContentRepositoryAdaptor. 
So it now works with alias names for getting Configuration when an index is created. When no index
name is given by another package the old behavior will
be used.
Merge pull request #18 from Flowpack/indexsettings

[FEATURE] index creation with index settings (to support aliases in CR adaptor)