Updated language design FAQ

I just added a bunch of new material to the language design FAQ. This document is necessarily opinionated, since by nature it represents our reasons for designing this language the way we did, but I've tried to keep it as objective as possible. Of course, aesthetic considerations are always also important in the design of any language, library, or framework.

I've added several new sections about the type system, including material on:

Please help me out here: what's missing from this document? What questions do you have about Ceylon aren't answered here? Which responses don't make sense?