Work around broken rotation in older GLM versions
Move GLM_FORCE_RADIANS def to CMakeLists.txt

That's the proper place for things that need to be defined before the
first include of a library.
Move glm/gtx/transform.hpp out of MathFwd.h
Remove glm/gtc/quaternion.hpp inc from MathFwd.h
Move vector functions out of MathFwd.h
Fix indentation in Rectangle.h
README.md: Document GLM dependency
Move glm/gtx/euler_angles.hpp inc out of MathFwd.h
Remove glm/gtc/matrix_transform.hpp from MathFwd.h
Move glm/gtc/type_ptr.hpp inc out of MathFwd.h
Rename math/MathFwd.h to math/Types.h

It no longer just forward declares stuff.
Merge math/Vector2.h into math/Vector.h
Merge math/Vector3.h into math/Vector.h
CMake: Add debug output flag to build type summary