Improvements of an assorted sort

Fixed compatibility with kicad testing build, new features:

• Improved eagle zone and variants handling
• Tented/untented vias support (kicad/eagle/generic parser)
• Collapsible top bar to save space
• Native kicad dnp field support

As always, thanks to @Funkenjaeger for continued work on eagle support.

Notable commits:

• 7cf646f Add toggle to hide top bar
• 865cab9 Fix compatibility with future kicad testing build
• 630301b Implement untented vias for kicad
• a05f4ac Initial provisions for un-tented vias (fusion/eagle)
• 77eb20b Fix handling of complex polygonpours, don't process polygons to zones
• 07a3d20 (Eagle) Fix handling of DNP's via assembly variant
• f918435 Add kicad 7 native dnp field support