Add additional bootloader commands.

[whoenig]

The following commands are added: AllOff (full power-off), SysOff (STM32 off), SysOn (STM32 on), GetVBat (check battery status without turning STM32 on).

We use those commands within the Crazyswarm project to put all CFs in power-saving mode while they are not in use, and to perform fast battery checks to identify CFs which need a new battery. So far, the commands are supported within the crazyflie_tools of the crazyflie_ros package.
With this change, the Crazyswarm can operate on the latest official radio and nrf51 firmwares:-)

Is there any wiki page where those commands should be documented?

[ataffanel]

Thanks! This is great. I tested and pushed it. Do you have any measure of the power consumption of the radio alone? I guess there is potential for improvement in the NRF power consumption when the system is off.

The bootloader protocol is documented there: https://wiki.bitcraze.io/doc:crazyflie:bootloader:protocol.

[whoenig]

Thanks Arnaud! I updated the wiki with the new commands. Unfortunately, we didn't do any scientific measurements of the power consumption. All I can say is that in power-save mode, we can leave the CFs for 1+ hour on the ground and then still fly without issues, while when keeping the STM32 (and LED deck) on, the battery will be empty after maybe 30min. Also, in our experiments we used an older NRF firmware and I believe you recently fixed a few power-related issues; thus, the current behavior might be even better.