Add an easy mechanism to add arbitrary phases

## 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 `Future`s that could be listened to might be helpful here? It would be nice of `Component`s 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.