moving more fct_1d logic from the solver to the formulae file
introducing 4 subdirectories in the solvers directory: adv, adv+rhs, adv+rhs+vip, adv+rhs+vip+prs
adding missing cdots in doc.hpp
Merge https://github.com/slayoo/libmpdataxx
Merge branch 'master' of git://github.com/trontrytel/libmpdataxx
fixes to fct by Ania - now it works like a charm!
Merge https://github.com/slayoo/libmpdataxx
fixed velocity extrapolation - bombel works