Add Display Settings to Footprint Browser.
Make each of them OpenGL on OSX and Cairo on other platforms.
Allow auto-zoom to be turned off and save last zoom setting.
Make ordering of tools in htoolbar consistent.
Standardize grid and zoom drop-downs.
Fixes: lp:1791667
* https://bugs.launchpad.net/kicad/+bug/1791667
There's no point in having both Save Symbol and Save Library when
only one can be selected at a time.
Also cleans up a bunch of extraneous icons, and fixes a few
copy/paste errors in menus and toolbars.