Add double-precision vector and matrix classes

Add double-precision versions of Vector3D, Point3D and Matrix3D
classes. Add new file sreDoubleMath.h.

Correct order of argument names for Matrix3d::Get.

Signed-off-by: Harm Hanemaaijer <fgenfb@yahoo.com>
Tweak physics control object velocity handling

Signed-off-by: Harm Hanemaaijer <fgenfb@yahoo.com>