The "Author" struct was too overloaded in different types of queries that treat struct fields in incompatible ways. This change defines a simpler CommentAuthor struct for use in comments until we can figure out how to query `... on User` information for comments too.
- `issue comment` no longer fetches all issue fields and thus avoids the
problem when loading failed due to token not having access to projects
- `issue comment` now accepts either issue or pull number as argument.
This removes sensitivity to the BROWSER environment variable in tests
and makes it easier to verify the URL that the browser was invoked with
without having to stub sub-processes.
