Clarify the HTTP status codes

[johnbillion]

A client has been adding mostly 307 redirects as its description is closest to what they want ("Temporary Redirect") but a 302 is more appropriate most of the time.

The status code dropdown, and its descriptive text, should be improved to make it clear that most of the time a 301 or 302 is preferred.

See also #68 for discussion about the non-redirect status codes.

[rmccue]

307 is basically a replacement for 302, so it should be appropriate in all cases anyway, but the wording probably could be clearer.