(PDOC-3) Refactor face and remove modules action

Refactor the code in the strings face and extract much of the functionality
into a separate library in order to make the code more readable and
sustainable. Additionally, remove the `modules` action from the face
since it does not have a clear use case currently. However since the `server`
action depends on it, and it may be helpful to add other features in the future,
extract the functionality previously contained in `modules` into a helper
method.