Merged form factor material decorators into FormFactorDecoratorMaterial (for both matrix and scalar materials); moved matrix evaluate to IFormFactor; removed FormFactorPol

Refactor: rename form factor decorators containing material information to FormFactorDecoratorScalarMaterial and FormFactorDecoratorMatrixMaterial

Refactored FormFactor chain: transformation now sits in Particle; wavevector scattering factor and scattering density reside in the same class (FormFactorDecoratorRefractiveIndex and FormFactorDecoratorMaterial for scalar and matrix scattering respectively)

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)