Hydro_RNSID should not inherit from GRHydro

[Zach Etienne]

Hydro_RNSID will not compile without GRHydro, as apparently it inherits some variable(s) from GRHydro. Being a hydro initial data thorn, it should only depend on HydroBase & ADMBase.

Keyword: Hydro_RNSID

[Roland Haas]

Pull request which removes GRHydro dependency is here: https://bitbucket.org/einsteintoolkit/einsteininitialdata/pull-requests/4/hydro_rnsid-remove-dependency-on-grhydro/diff

This so far is untested and while in principle there should be no change in data since GRHydro alsready schedules an InitialPrim2Con routine there may be differences in the atmosphere treatment and / or for past timelevels.