Add an easy mechanism to add arbitrary phases

[mkorbel1]

Motivation

It would be nice to offer the ability for users to add any number of arbitrary phases as needed for their project.

Desired solution

Perhaps some Futures that could be listened to might be helpful here? It would be nice of Components could detect if a desired phase never got registered? Should all new phases be part of (subphases of) the run phase? It requires some thought for a nice API to implement this.