fix(server): add user facing remove API

This was accidently removed as we refactored the standy stuff. Re-add this
user facing remove endpoint that matches the config endpoints.
fix(Documentation): update based on standby refactor

These docs were not updated after the refactoring of the standy mode.
Fix that now.
feat(Documentation): document the entire admin machines API

Flesh out this document a bit more completely.
Merge pull request #806 from philips/add-machine-api-docs

fix(server): add user facing remove API