MSVC: switch to boost::time instead of linux time, RootMinimizers now compiled as static, switch to MathFunctions::isnan in functional tests

Beam's alpha_i value can also be given as positive value now (internally it needs to be <=0 for incoming beams)

Changed convention for passing two doubles to define refractive indices: now n = 1 - delta + i beta (delta, beta are the two parameters)