Simplify Allen accesses to ParamFiles and enable versioning

!812 (merged) moved parameter files to ParamFiles but left multiple locations where the same filename has to be specified notably Rec/Allen/RunAllen.cpp and main/src/Allen.cpp (the former is now Rec/Allen/ProvideConstants.cpp in master)

Having to keep these in sync for any given released version is fragile and the relevant filenames should be specified only once to enable robust versioning.