Updating user guide; allowing optional server rename during rebuild.

Most of the changes are lowercasing the method names in the documentation to make them consistent with the code.

Other changes include:
* Documenting that `$adminPass` is required when rebuilding the server.
* Un-documenting that a new `$flavor` can be specified when rebuilding the server.
* Updating the names of the reboot state constants in the documentation.
* Fixing the code for the `Server::rebuild()` method to optionally pass through a new server name.