2D paths do not snap to the plane of the parent Transform

[mrpropellers]

When the space specified is on a 2-dimensional plane, the path snaps to the global 0 coordinate for the axis that is being ignored, rather than the local coordinate of the parent object. This means that if a user wants to create a path that is constrained to a 2-dimensional plane, they are obliged to do so in global space and then switch to 3d coordinates to move the path, rather than building the path in the parent transform's coordinate space. It also means the path jumps around quite a lot when the parent game object is far from the scene origin and a users is switching between path spaces.