Added Changelog Management System.

A frequent problem on all SS13 codebases is keeping the changelog up to date, as the changelog is a horrible nightmare of bad HTML.  On top of this, pull requests that modify the changelog often cause merge conflicts.  For this reason, codebases without a strict update process don't bother updating the changelog.

To solve this, we at /vg/ propose this system, which decentralizes the changelog entries by developers into one changelog per developer (reducing the chance of a conflict), AND simplifies them into YAML, which is far simpler for git to handle.

Changelog *generation* is now performed centrally after a batch of PRs are pulled, and the system automatically generates HTML and timestamps everything.  A central "database" also keeps track of all changes to prevent duplication and allow further updates to be added to the same date, without creating a mess.  A templating system is also installed, to allow some customization of the output product without having to dig around in the python code.

 * Port requested by Cheridan.
 * Timestamp system has been updated to handle /tg/'s special snowflake timestamp format.
 * I've also had to fix some typos in the changelog itself in order to get the dates to parse, otherwise, b(e)yond some indenting changes and comment removal, it's identical to the old changelog.
 * Python 2.7 is required to run the genchangelog tool, as is PyYaml and BeautifulSoup 4.
 * And yes, I tested this, for once.
Fix empty author records being written.
Add delete-after directive, updated docs.
Merge branch 'master' of https://github.com/tgstation/-tg-station into changelog-mgmt
Updated changelog data.
Merge branch 'master' of https://github.com/tgstation/-tg-station into changelog-mgmt
Updated changelog data, fix merge conflicts.
aliums 2spukki
more icons for stuff, nightvision for aliens with hud icon button and toggle verb
awful awful table smoothing pasta replaced with smoothwall modification
no more hideous smoothtable shit
cleanup
fixed larva night vision
qdel
fixed icons not changing on wall destruction
nest pixel_x adjusted
egg click cooldown fixed, HEADCOVERSMOUTH removed from inappropriate items
fixes aliens resting/crit sprites
facehuggers won't attack an infected person
Changeling Hivemind Communication Costs 1 DNA

- A new Hivemind Communication power is required to be purchased before the changeling can use the changeling channel (:g)
- Changelings without the Communication power can still faintly sense if other changelings are speaking through hivemind.

Remove changeling kill-teams. Add paranoia and ling vs ling conflict.