simplify class CParam<Param_t>

[qPCR4vir]

Currently it can accept a reference to the used simple program parameter. But this complicate this clase, causing code duplication and introducing many nuances for it use: with the get() or directly, or even creating dangling references. It also have an internal value, "just in case" no external reference is passed. We better make this case the only available, so this will be the only place where the parameter is. It also introduce possible value duplication in base classes