make a website name / domain name config and use it consistently

[9san]

I can make site creation much simpler by making all mentions of the site, and domain for emails, be pulled from a config allowing it to be much easier to personalize for imageboard hosting.

Config examples:

$config['website_name'] = '9channel';
$config['domain_name'] = '9san.ch';

Template examples:

Welcome to {{ config.website_name }}!
Please contact admin@{{ config.domain_name }}.

I haven't even changed everything myself, there are some stuff that's slipped by me (such as profile editing for mods still listing @8chan.co.