Universal properties without funext, and localization

See <http://homotopytypetheory.org/2014/11/02/universal-properties-without-function-extensionality/> for a detailed description of the contents of this PR.
Hmm, I guess that with this definition, `Op'` technically does depend on funext.  But this definition ends up equal to `Nul (fun (_:Unit) => U)`', which doesn't.  Maybe I should define it as the latter, outside the section.