Moved menu to heap; 2048 memory fix; back to normal vfprintf

Menu:
  Prevent running out of data memory by moving menu to use heap allocation.
  Removed ALLOW_RETURN_ROOT, moved this to user code:
    Disallow "out-of-bounds" cursor when navigating upwards in the menu.
  Fixed a bug in menu_depth()

2048:
  Fixed a memory leak.
  Removed UART actuator.

Linker:
  Moved back to normal vfprintf, as left/right justify was not supported.

Current memory usage:
  Program: 99.8%
  Data: 55.9%
  EEPROM: 41%