* Refresh the view only when changes are made in the caller frame.
* Allows recreate a new instances when try to open the 3D view from a frame taht is not the initial caller
* Remove duplicate code in kicad frames.
Frame, dialog and config file couldn't agree on whether to use
internal units or not.
Frame now stores internal units, and they're now mapped on the
way in/out of the config file. Dialog was already assuming they
were stored in internal units (though they were previuosly not).
Fixes: lp:1751435
* https://bugs.launchpad.net/kicad/+bug/1751435
Also adds indicators in layers palette for feedback.
Also generates sized images for all indicators instead of using
scaled bitmaps (which didn't look great).
Also fixes a completely unrelated typo in a UI string.