adding OvMaths::FMatrix4::Rotation and OvMaths::FMatrix4::Rotate

[kmqwerty]

Contributes to #92

[adriengivry]

If you forward declare FQuaternion because of circular reference, this include should get moved to the .cpp file.

[adriengivry]

This isn't necessary as FMatrix4. is already included.
It can be either removed, or we can move #include "OvMaths/FMatrix4.h" from this file to the .cpp file.

[adriengivry]

Looks good overall! I've noted a couple of stuff that we should fix.

Morehover, in the future, it would be good to forward declare everything that we can in header files, and move all our includes from header to source files.
This was a bad practice that I wasn't aware of at the time most of Overload code/architecture has been made. As a rule of thumb, never include other header files from a header file, unless you are implementing some inline stuff that requires knowing more than just the symbol.

Thanks for your contribution tho, it's greatly appreciated :)

[adriengivry]

One other thing, this doesn't resolves #92 as this issue requires exposing these new methods to lua.

[adriengivry]

Looks great!