This commits gets rid of the extra external directory to unpack mu-plugins.
They are instead directly extracted into wp-content/mu-plugins/{name}/, and then the relevant files are copied
(via the drop-in mechanism) to wp-content/mu-plugins/. This leaves spurious directories with undeeded files (readme, composer conf, etc.),
but they should be harmless.

the Drop-in mechanism does not need to specify a file-name, in which case it copies all files (excluding readme.txt and similars). Slightly less stuff to write in this case: plugins which declare themselfs to be mu-plugins will be handled automaticaly, the ones which do not have to be listed twice.

More-privacy-option plugin actually ships with other files (translations), so it should not be considered a mu-plugin, but installed network wide as a regular plugin.

Now merged in /noblogs/ai-buddypress-plugin.

child themes are not in this repo anymore, they should all go into
noblogs/themes-child

KaTeX is a LaTeX plugin and js library which should be ligher, smaller, faster, but less complete than MathJax (which is what we were using so far). It might be worth to try it as an alternative (I don't think there is heavy usage of Latex on noblogs).

Clean up the HyperDB patches

See merge request !1

These patches only touch configuration files, and we have those
shipped as part of the container in ai3/docker/noblogs!6.

Fixes issue #2.

Closes #6