all remaining submodules are now non-essential to running a server.
They are also versioned and updates can be done automatically using 'composer update'.
Finally, we can also put an end to the issue of translations being rendered incorrectly or being missing due to outdated submodules.
Sacrifice dynamic composer autoloader path to do this, because we don't
need it anyway - it was a misconceived feature from the days when I used
the same workspace for PM3 and PM4 both.
