nixos: Try to show an helpful message when the user sets config. or options.

Feel free to improve or remove :-)
pbzip2: update package
gitolite: add dataDir
Merge pull request #4773 from abbradar/gitolite-home

gitolite: 'dataDir' option
Merge pull request #4771 from abbradar/pbzip2-update

pbzip2: update package
Bump git-repo to 1.21

Still no versioned URL, but there’s been a new release. SHA1 pulled
from http://source.android.com/source/downloading.html#installing-repo.
Merge pull request #4775 from ajbouh/master

Bump git-repo to 1.21
pidgin-latex: replace with SF one and fix
monthly bump of dolphinEmuMaster

also dolphinEmu and dolphinEmuMaster had an extraneous stdenv removed
from buildInputs
Merge pull request #4776 from abbradar/pidgin-latex

pidgin-latex: replace with SF one and fix
nixos/modules/services/monitoring/graphite.nix: don't create graphite user unconditionally

I'm not sure what exactly this user is needed for, i.e. under what circumstances
it must exist or not, but creating it unconditionally seems like the wrong thing
to do. I complained to @offlinehacker about this on Github, but got no response
for a week or so. I'm disabling the extraUsers bit to put out the fire, and now
hope that someone who actually knows about Graphite implements a proper solution
later.
nixos/modules/services/monitoring/graphite.nix: strip trailing whitespace