Merge remote-tracking branch 'firmware_AIDA/master'

Used instructions at https://bneijt.nl/blog/post/merge-a-subdirectory-of-another-repository-with-git/ to merge in Paolo's firmware with FMC-TLU Git repository

git clone git@github.com:DavidCussans/firmware_AIDA.git
git clone ssh://git@ohwr.org/fmc-projects/fmc-mtlu.git
cd fmc-mtlu/
git remote add firmware_AIDA ../firmware_AIDA
git fetch firmware_AIDA
git merge -s ours --no-commit --allow-unrelated-histories firmware_AIDA/master
( N.B. Had to add allow-unrelated-histories flag ... )
git read-tree --prefix=AIDA_tlu -u firmware_AIDA/master
git commit