[ground_segment] fix green->darkgreen change

Since tcl8.6 "green" refers to same color as "darkgreen" (to the one used in web) and the former "green" is now "lime"...
But "lime" is not available in older versions, so hardcode the color to #00ff00
[messages] replace BOOT with AUTOPILOT_VERSION
[gcs] log autopilot version in alert window once
[gcs] remember version per aircraft
[test] test_ms2100: replace BOOT with TAKEOFF message
[build] add build version to the log and print warning if not matching runtime version
[build] improve build version stuff

- always save build version when updating anything that depends on libpprz, so it will also be updated on e.g. make tmtc
- only warn if the version number (major.minor.patch) is different, disregard the label, sha1, dirty postfixes in the string...
[server] close file even if file empty