Curve Behaviour: set curve shape and strength when Alt+drag/rotate_vertices_selection

This feature should give the opportunity to determine -with two or more sliders, or path based- the curve shape that influences a selection of Alt+dragged vertices -default: gaussian; for now this control is only achieved by pressure of a graphic pen. The Curve Behaviour should also be applied when Alt+rotating a selection of vertices, giving maximum movement towards the center of rotation. A strength/area parameter should determine how much neighbours are influenced, optionally using visual feedback with red to blue vertices colouring. When Alt+dragging, user should be able to point'n'drag from a blank area, not just from a selected vertex. Curve shape could be Asymmetrical on x-axis allowing more deforming possibilities. Users can save to a presets library. A final thought: when moving, vertices deformation could optionally follow the entire cursor path instead of the straight line that is drawn between the start dragging point and the release one.