Add configurator.getRetrievers
Add configurator.getRetrievers

Hides the fact that we changed the syntax of the retriever services
a bit.

alpheios-project/arethusa,PonteIneptique/arethusa,fbaumgardt/arethusa,PonteIneptique/arethusa,fbaumgardt/arethusa,alpheios-project/arethusa,Masoumeh/arethusa,alpheios-project/arethusa,Masoumeh/arethusa,fbaumgardt/arethusa,latin-language-toolkit/arethusa,latin-language-toolkit/arethusa