[CMAKE][CORE] Move WWSaveLoad and most of WWMath to Core

[xezon]

• Closes [CMAKE][CORE] Move WWSaveLoad and WWMath to Core #681

This change moves WWSaveLoad and most of WWMath to Core and is an alternative to #681.

The following files of WWMath are not moved to core yet:

• cardinalspline.cpp
• colmathaabox.cpp
• colmathaabtri.cpp
• colmathobbobb.cpp
• colmathobbtri.cpp

They can be moved once unification is sorted.