Merge pull request #359 from Coeuvre/master

Made some functions to inlined
Removed `PixelRectangle` from `Image`
Changed `Vec2d` to `&Vec2d` for consistency
Changed from `Ray` to `&Ray` for consistency
Added `HasViewTransform` to `internal`
Added `CanViewTransform` to `internal`
Changed to blanket implementation for `View`
Removed `Vec2d`