path alias processor needs to document that access on the server is needed

Problem/Motivation

The path alias processor fails if the server user doesn't have the 'administer url aliases' permission.

The UI should tell users about this -- say that either that permission is required, or some other way of granting access to view path alias entities.

I'm going to make a quick contrib module that does this.

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes