BIS78 RPC - Add cabling alg & tester

Hi everybody,

this MR implements the next step towards implementing the BIS78 RPCs into the ATLAS EDM, namely the cabling creation alg + a testing routine + a script that creates a dummy JSON file to be used in simulation and also into the database.

@formica proposed that the most convenient solution in terms of database & also of human readability would be the creation of a JSON file. A script to create such a file is added in this MR and can be executed via:

python -m MuonNRPC_Cabling.createCablingJSON

Of course, the changes have to be compiled beforehand. I'm asking @mnegrini, @lpizzime, @mcorradi, @apolini to take a look at the layout of the produced JSON to tell me whether it's vital. Hence, review-pending-expert is explicitly required for this MR. Once the confirmation of the format arrived, I propose to accept this MR and prepare the database folder in parallel.

The MuonNRPC_CablingAlg retrieves the JSON file either from the database or from an external source

The MuonRPCCablingTester loops over all BIS78 channels, as given by the readoutgeometry, converts the offline Identifier into an online cabling object -> and then back to the offline identifier. Initial and final Identifier are required to be identical to pass the CI test.