This is mostly aiming at allowing us to fiddle with the mock FS during
tests.

This is more convenient to set a FK to null when it's unset, rather than
having to write 2 different insert statements

This also ensures we are using the absolute path instead of the user
provided one

It only does binding a nullptr to sqlite, since we can't write to a
nullptr, nor can we assign nullptr to int/string/float/...

Remove forced debug flag, let cmake add it if we build in debug mode
Add pedantic warning flag

Processing is done by a threadpool (limited to a single thread so far)
This will allow using asynchronous modules one after another
Fixing VLC service cleaup code