[SOFT-499] Upgrade CI to Ubuntu 18.04 (#413)

GitHub Actions phases out Ubuntu 16.04 at midnight, so we're upgrading less than half an hour before the deadline.

[SOFT-538] Remove references to old firmware repo, add GitHub Actions…

… to README (#439)

- the git hooks were trying to cd into the old firmware repo, update them to firmware_xiv
- DEVELOPING.md exists, and hadn't been updated since MSXII; update it
- update README.md to talk about GitHub Actions rather than Travis CI, which has been gone for a while

[SOFT-539] Fix CI certificate issue (#440)

For some reason, the fiam/arm-none-eabi-gcc action in CI was failing with a certificate issue. To fix it, we just install the arm-none-eabi toolchain ourselves instead of using the third-party action.

Also, added a copy of the nanopb license to libraries/nanopb so we don't violate any license terms.

added nanopb library and adjusted make files to ignore nanopb library…

… in linting/formatting. (#434)

* added nanopb library

* added quick-lint ignore

[SOFT-514] Improve MCI status broadcast (#433)

This improves the MCI status broadcast so it sends more useful info.

In short, SYSTEM_CAN_MESSAGE_MOTOR_STATUS now sends each WaveSculptor's status/limit flags, as well as any board overtemperatures and overtemperatures from the WaveSculptor's temperature messages (to be added in SOFT-534).

[SOFT-495] Migrate bootloader from protobuf-c to nanopb (#426)

Nanopb is a more embedded-friendly protobuf implementation, so we use it instead of protobuf-c.

[SOFT-530] Datagram testing module (#430)

[SOFT 421] Transmit motor temp (#408)

This adds transmitting motor temperature over CAN from MCI.

[SOFT-527] Update NTC thermistor curve (#428)

It now obeys the experimental curve rather than the theoretical one (commented out). See https://www.desmos.com/calculator/fqoelc5mkj.

[SOFT-516] Update steering: DRL behaviour (#425)