CaloGeoHelpers: A few additions to CaloSampling.
Add CaloSampling::getSampling to convert from a name to a sampling. Make getNumberOfSamplings() constexpr. Add a unit test for CaloSampling.
Add CaloSampling::getSampling to convert from a name to a sampling. Make getNumberOfSamplings() constexpr. Add a unit test for CaloSampling.