editing devices: arc tool

When positioning a device with arc:

[x] 1. the control points of the arc remain even after moving to free position and back (which should have cleared it).
[ ] 2. the control point of the length of the rc disappear and it is not possible to manipulate it.
[x] 3. The menu of the arc collides with the grid and other menu on the lower left side of the map.

argosp / trialdash