Implement support for easily determining what notifiers are enabled

[atc0005]

While implementing #21, I've setup a NotifyTeams() and NotifyEmail() pair of methods to determine whether those notification types are enabled. Unfortunately they're tied directly to a Config type, so only the value created from that type can be used to call the methods. This either means I pass the Config value to each part of the code that needs it, or I find a way to track and expose the state of all notifiers (enabled/disabled) from relevant parts of the code that need it.

For now, the stats output related to Teams (#21) and Email notifications (#19) will be generated regardless of whether they're actually used.