Separated Chebyshev3D classes to new MathUtils module, refinenments/fixes in MagneticWrappet
Removed unused mfchebKGI_meas.root version. Substituted mfchebKGI_sym.root by the version containing MagneticWrapperChebyshev objects instead of AliMagWrapCheb
using namespace AliceO2::MathUtils instead of explicit prefixing