Build site and pdf by default

[emillon]

Closes #3416

[emillon]

Building the html (the part that fails on the linked PR) requires pandoc, so we'll have to mark it as a depext. That will be easier to do once #3412 is ready.

[emillon]

In terms of dependencies, this requires pandoc and texlive-full.

For pandoc, depending conf-pandoc works (the version is different from the one installed in Dockerfile, 2.9-1 from github vs 2.2.1-3 from debian, though I haven't compared the output).

For texlive it's a bit more involved: there's conf-texlive but it does not install all the required packages (and the build fails with a missing xcolor package). Adding texlive-full in depexts work. I suppose we could add a conf-texlive-full package which attempts to build a document that uses xcolor.

[emillon]

Rebased and now green.

[avsm]

I've got a bunch of PDF changes queued up for the new format we need to give the publisher, so I'll close this one for now.