Minor for pydoc types.
Update pot generation command.
Complete ja, it, fr, nl, ru translations and fix a string.

Thanks to all translators.

There was a typo "infinite an infinite number..." I just keeped the
translations as they are very likely to be correct.

I also removed the location info in all translations (as we started
doing a while ago) and old strings not useful anymore.
Completed lt translation.

Thanks to Vytis Banaitis.
Added competitions in README and missing bs translations.
Add CEOI 2014 to testimonals.

Also fix some punctuation.
Stop services giving the same ID to all their sandboxes

This helps in case of task that require multiple sandboxes (like those
of Communication type) to reduce mutual interferences.
Doc about task versioning.
New testimonial.
Completed zh translation. Thanks to Yuan.
Proposal for detailed timing documentation.
Update documentation about running CMS.
Update documentation about creating contests.
Update documentation about configuring a contest.
Update documentation about task types.
Update documentation about external contest formats.
Update documentation about RWS.
Update documentation about localization.
Update documentation about troubleshooting.
Update documentation about CMS internals.