Mayhem firmware

Changes:

• Renaming the fork to Mayhem, to keep new Releases centralized
• By popular demand: "Play dead" and non-implemented features removed
• Tweaks in the layout of the UI, new font, splash and new set of icons
• Releases will use major.minor.revision semantic versioning now, and the version appears on the titlebar; no more guessing which version is the newest
• From previous revisions:
  • Improved world_map.bin, using a new Mercator map
  • GPS sim, including some samples
  • New receivers: BLE, Nrf, analog TV
  • Debug app back from original Portapack

Bugfixes:

• Fixed several system halting problems, specially when exiting/entering some sequences of apps
• Backlight timeout works better
• Minor improvements