Add more "ergonomic" functions for safely constructing URLs

[andywhite37]

Right now, there is a lot of type/constructor heaviness in the APIs, so it would be nice to have a more friendly set of functions for safely constructing and manipulating URLs.

The goal would be to have a recommended way to "parse" a URL into our data structure using a string (and return an Option/Result), and a goal to safely construct a URL from it's parts in a nice clean way, which would ideally not require the use of Option/Result. However, since most parts of the URL are strings, it becomes hard to guarantee that the URL is valid and not use Option/Result (or throw exceptions).

We'll always have the parseExn style API for URLs, but if we can avoid that being the default use-case, it would be best.