Add binomial random number generator with cached probabilities for fixed p: RandBinomialFixedP

The TRT digitization code uses binomial random numbers with a fixed probability. This code provides a variant of CLHEP::RandBinomial that avoids thread local variables and caches binomial random numbers for a fixed probability and this way speeds digitization up by ~10%. The static shoot(...) methods are all disabled, as the caching only works with an instantiated instance of RandBinomialFixedP