Porting prep: Move settings and general logic to plain C++

[attah]

Move as much logic as possible from JavaScript to C++ and SeaPrint to ppm2pwg.

• Format support checking/listing
• Format conversion logic
• Print job settings (beyond pure input)
• Name-prettification
• WiFi Checker
• App settings (and make backends swappable)
• Everything backing the properties page
• Debug JSON
• Fake-printers
• Saving of default job settings