dropping files to Kicad manager :
*.kicad_pro, *.pro -> open project;
gerber and job files -> open in Gerbview editor;
Eagle and Cadstar files -> open project.
dropping file to schematic editor -> append schematic;
dropping library file to Symbol editor -> add library;
dropping board file to PCB editor -> append board;
dropping library or footprint file to Footprint editor -> add library or import footprint;
dropping ZIP file or gerber files to Gerbview editor -> open files;
dropping sheet file to Drawing Sheet editor -> open sheet.
Fixes https://gitlab.com/kicad/code/kicad/-/issues/11638
Particularly important on Mac where the menubar is disabled when the
frame is used in modal mode.
Also adds a display control to override the symbol's show pin numbers
setting.
Fixes https://gitlab.com/kicad/code/kicad/issues/7789
Some differences are due to difference between libraries being files
in symbol editor and directories in footprint editor, but this unifies
most of the rest.
It also dispenses with the save-to-library vs save-to-document distinction
in the GUI because it makes for too much variability in the GUI, was
implemented differently between the two editors, and isn't needed as much
anymore now that we have the highly visible infobar.
There was also an issue that the save-to-board icon occupies the same
location and has the same size/shape/colours as the Board Setup icon in
PCBNew.
Fixes https://gitlab.com/kicad/code/kicad/issues/7215
Jon Evans
lulu731
Jeff Young
Wayne Stambaugh