add dynamic and static methods for factorials and binomials

@carsten.graeser I had some problems with constexpr functions where the loop variable is supplied as an argument with gcc5 in the past. Also the range method is not declared constexpr (despite the constructor of the implementations being constexpr).

Replacing the use of range() by a plain good old for loop still seems to be a much better solution compared to those seven template specializations. I cannot see the loop variable passed as an argument anywhere.

I also vaguely remember that caching binomials gave a significant performance improvement in some applications. This is of course only possible for moderately sized arguments and would need some benchmarking.

I meant the loop bound not the loop variable. I will check if the simplified version works.

resolved all discussions

@carsten.graeser Since the version you suggested works on all compilers that support a reasonable amount of c++14 I changed the implementation.

@janick.gerstenberger: The question is, if the list of those compilers is a superset of the compiler we support in master.

@carsten.graeser it works with gcc5+, clang3.5+. icc18.0 appears to work in godbolt. if i remember the meeting notes correctly that should cover the master and 2.6 .