Sends token & comment when the chat session starts

Sends token and comment of the related ticket to the support assistant
at the start of the chat session without sending them to the user's web
UI.
using .text() instead of .html() to prevent xss attacks
Swapped variables for constants in prodromus.js
using django's slice instead of truncatechars
using <a> instead of <span> for links
Using @staticmethod instead of instantiating Token() objects
removed Token.get_token()
Implements Stats

Stats is a client-side tool that helps support teams report what
kind questions they answer and their frequency.
pups/home now reports personal user stats
pep8 cleaning
Fixes pups' CSS

Pup' CSS was all over the place, this commit gathers all the scattered
pieces and puts them into pups.css
Updates README.md
[#12625] Stops prodromus from eating http/https links

The webchat UI previously ate http/https from links as a form of
simplifying/beautifying urls but that proved bad when users copy/pasted
logs so now it displays full links instead of simpler ones.
Adds a stats monthly backup custom command.
Prevents a user from locking an issue indefinitely.

Previously, Stats gave users the right to lock issues indefinitely with
no expiration. This commit fixes that by settings a timer on each lock,
if the user takes more time than the one set in settings.CONFIG, his
page will refresh and unlock the issue for others to edit.
[#12626] Fixes multi-line support in webchat