Refactor Greenlock implementation

[KenEucker]

We should be using greenlock.manager.add instead of generating the config.json ourselves, per the docs:

You should NOT edit greenlock.d/config.json with your own tools. Use greenlock.manager.add({}) instead.

With this, we should also refactor the host option to be able to accept an array of acceptable hosts. This will help in supporting biketag.us alongside biketag.org and biketag.ca while paving the way for us to break out each of those servers and provide dynamic webhead load balancing.