Outline mode can be set up on any layer.

Ratsnest is updated after exporting changes from the module editor to the layout editor.

Introduced SELECTION_CONDITIONS to determine which menu entries should be visible in the SELECTION_TOOL context menu, depending on the selection.

- zone filling algorithm
- printing
- plotting (pdf & gerbers)
- SVG export
- Specctra export
- 3D viewer

Created dialog_dxf_import.h. Cleaned up some unnecessary stuff and fixed file open dialog DIALOG_DXF_IMPORT.