The router preview item can be specific to the part that is being
tuned, rather than the whole net. It's also less visually noisy as
it doesn't dim/undim the rest of the board.
Using kigfx preview items for the status keeps us from having a bunch
of focus issues with the status popup window.
Use standard Magnetize() to handle grid and magnetic pads.
Use the standard menu from PCB_TOOL. Delegating the menu to
the SELECTION_TOOL just caused grief.
Also brings clients (such as Position Relative To) into line,
and implements better Cancel behaviour.
Also improves visibility of modal status messages:
- moves Select Anchor message from status bar to popup
- moves Select Reference message from dialog to popup
Fixes: lp:1786727
* https://bugs.launchpad.net/kicad/+bug/1786727
1) hide the status popup when the dialog is brought up
2) forward events from the popup to the canvas so hotkeys work
3) make sure diff pair radius is always 100%
4) fix greyed-out Miter style label
5) make L a hotkey so it works before you start dragging
Fixes: lp:1545856
* https://bugs.launchpad.net/kicad/+bug/1545856