Support for UV Stretching overlay during multi object editing. The VBO now holds the ratios per fase. In the shader these ratios will be compared against the global ratios. The global rations are created from all selected objects. The current implementation does not fit well with the draw module. The plan is to move the drawing of other spaces towards the draw manager what leads to a better fit. Currently the details on this solution is unclear but this requirement will become an attentionpoint in the future design. Reviewed By: fclem Differential Revision: https://developer.blender.org/D5665