Killing off some especially uptight rules

After some polite debate on IRC I've removed a few of the more persnickety rules that don't really matter much and a few others that just don't need to be spelled out. Unclenching.
For fully qualified URIs, yes. This really only applies if there's a domain, and that really only applies to outside sources. A file-relative or root-relative URI is better for local resources, and those never have a protocol anyway.