Dossiers own reference prefix adapter.

At the moment the dossiers and repository refernceprefix numbers are mixed up. That cause some problems when trying to split repositoryfolder, which contained dossiers, in to two single subrepositoryfolders.

For this reason it's necessary that dossier types use their own reference prefix adapter. The PR contains the following adjustments:
* Refactoring of the reference prefix adapter tests.
* Reworked reference prefix adapter: use now two different counters for repository and dossier types.
* Upgradestep which cleanup the mixed up refrence prefix mappings.

@lukasgraf @jone could you take a look?

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