Improve curved wire control

[KjellMorgenstern]

Problem

Curved wires are hard to control.

If a curved wire is selected, we don't yet show indicator lines or bezier points.
These become only visible when dragging the curved wires started.
Bezier points can not be directly seen or dragged with the mouse or keyboard.
When modifying a curved wire, the mouse is fixed to the wire, and align to grid limits mouse positions.
If I want clean, symmetric, aligned curves, I always turn of align to grid, and carefully watch the indicator line to end on a grid point. This is quite cumbersome.

Idea

Bezier points should be selectable
Bezier points should be visible when a curved wire is selected.

Align to grid should control the bezier points, even if we are dragging the wire, not the bezier point.

Holding shift should move the bezier points along lines in 45 degree steps to the line between the wires endpoints. It might also make sense to make this the default, and use either the grid distance along the line, or some non linear stepping.