Allow httpd subservices to set the document root

Only the main service OR one of the subservices can set the document
root. This is used by mediawiki when it is hosted at the root of the
vhost.
Mediawiki: Add some needed rewrites
Add hspec-expectations-lens haskell package
Add libjenkins haskell package
scotty: jailbreak

Needed when overriding aeson to the new version, which in turn is needed
if using scotty on a project that also uses lens 4.0.
Merge branch 'biber' into installed-next
add mathematica-9.0.1
Build numpy against openblas
Don't set a default version of Mathematica

Nixpkgs should not set a default version of Mathematica. Many users of
Mathematica have institutional licenses and do not have immediate access
to new versions. If there is a default version in Nixpkgs, updating that
version will cause trouble for all such users.
Merge branch 'mathematica' into installed-next
Merge branch 'vobsub2srt' into installed-next
Merge branch 'zsh' into installed-next