Adds "UpdatePreferences" action that is called when the preferences are
updated, allowing running tools to act on changes that may affect them
Fixes https://gitlab.com/kicad/code/kicad/issues/9737
* Make the ruler able to switch to mils after creation
* Cleanup an unused flag in Pcbnew dimensions
* Move unit changed notification into EDA_DRAW_FRAME so more
frames to use it.
* Allow switching units when GerbView ruler tool is active
This uses the two-point geometry manager to split the logic of the ruler
geometry and the preview item display. This allows the ruler to use that
manager's angle snap feature.
This allows to measure between features on a PCB. It uses a preview
EDA_ITEM in common, but due to the use of the IDs, it's currently
Pcbnew/Modedit only.
This also adds several "utils" for graphical functons useful when
drawing preview items on GAL canvases.
Fixes: lp:1467313
* https://bugs.launchpad.net/kicad/+bug/1467313