Updates the code to use the new reporters_db. See upgrade.txt!

Adds a new dependency that will need to be installed. Some risk of citation algo being broken, but tests should catch any of these problems.
Adds a new stat to the homepage with upgrades to the naturalduration template filter.

"naturalduration" converts a number to either a dict of days, hours, minutes and seconds (months, years and milliseconds not supported) or to a colon-separated string as in the search results. This commit contains tests for this filter and upgrades to make it support dicts and weird values like 0, None or floats.
Tweaks.