New bootrom

New bootrom
+ Add common area at end of RAM to communicate between main os and bootrom
+ Lower stack end to make room for common area
+ Implement CMD_DEVICE_INFO in both OS and bootrom to give information about the current state and supported features
+ Allow hands-free firmware update: When CMD_START_FLASH is received over USB in OS mode, the device will reset and enter the bootrom
  Pressing the button in hands-free update mode takes precedence: releasing the button will immediately abort firmware update and
  perform a reset. Do not press the button.
+ Require each flash sequence to be preceded by a CMD_START_FLASH to set up the boundaries for the following flash sequence
  Not compatible with linux flasher before SVN revision 200
  Currently no compatible flasher for Windows. WINDOWS USERS: DO NOT UPDATE YOUR BOOTROM YET
+ Protect bootrom flash area unless magic unlock sequence is given in CMD_START_FLASH