Add documentation

[EdwardHinkle]

An attempt to group what information might want to be documented for the future when this opens up to a broader audience.

• Setting up config file (lib/config.template.php)
• Importing database (schema/schema.sql)
• Manually adding a user with random string token
• Setting cron.php to run via cron
• Upstart dependency and setting up the watchtower.conf script

[aaronpk]

@dg01d did a great writeup here: https://ascraeus.org/websub-part-i-watchtower/