#39 Selection and editing of multiple surface points

[Jonas Hörnstein]

Selection of multiple points is only available for bezier curves, and needs to be implemented for the surface model as well

[Håvard N. Jakobsen]

Would be good if we could use the same boardcommands for this as for bezier boards. If we have a common AbstractPoint base class this should be doable. Note that if we make a meshboard the same commands should be usable on that type of board. In addition we might want to make more edit mode commands (stretch, rotate, spiral, etc.) which may be essential for a meshboard but also useful for other types of boards/models