px4io: add safety_arm and safety_disarm commands
px4io: add safety_arm and safety_disarm commands

This will be used to make updating firmware on boot for vehicles with
no safety switch possible without power cycling. The startup script
needs to be able to force safety on to allow the reboot to work.

krbeverx/Firmware,jlecoeur/Firmware,mje-nz/PX4-Firmware,acfloria/Firmware,acfloria/Firmware,jlecoeur/Firmware,Aerotenna/Firmware,Aerotenna/Firmware,dagar/Firmware,krbeverx/Firmware,mcgill-robotics/Firmware,mje-nz/PX4-Firmware,PX4/Firmware,mcgill-robotics/Firmware,jlecoeur/Firmware,mcgill-robotics/Firmware,PX4/Firmware,PX4/Firmware,jlecoeur/Firmware,acfloria/Firmware,jlecoeur/Firmware,krbeverx/Firmware,dagar/Firmware,mje-nz/PX4-Firmware,acfloria/Firmware,krbeverx/Firmware,Aerotenna/Firmware,jlecoeur/Firmware,mcgill-robotics/Firmware,dagar/Firmware,PX4/Firmware,dagar/Firmware,acfloria/Firmware,acfloria/Firmware,mcgill-robotics/Firmware,darknight-007/Firmware,krbeverx/Firmware,mje-nz/PX4-Firmware,darknight-007/Firmware,PX4/Firmware,Aerotenna/Firmware,mcgill-robotics/Firmware,dagar/Firmware,darknight-007/Firmware,jlecoeur/Firmware,krbeverx/Firmware,krbeverx/Firmware,mje-nz/PX4-Firmware,Aerotenna/Firmware,PX4/Firmware,acfloria/Firmware,Aerotenna/Firmware,jlecoeur/Firmware,mje-nz/PX4-Firmware,mcgill-robotics/Firmware,darknight-007/Firmware,dagar/Firmware,dagar/Firmware,PX4/Firmware,Aerotenna/Firmware,darknight-007/Firmware,mje-nz/PX4-Firmware