Removing of another <*stream> #include leads to more compilation time
saving, now from ~5:12 to ~4:55. Another compilation time improvements
will now be possible only by using Clang's modules, I don't know where
to optimize further (except for getting rid of <sstream> in tests).
Vector4 doesn't set W component to one by default anymore, this is now
handled by Point*D itself. This finally allows creating of 2D primitives
and 2D position vectors without messing explicitly with Z = 1.
All classes which should use Point instead of Vector were updated to use
Point instead.