URI docs and updated index

Looks like my last comment was:

> I'd like to change this to "view:&lt;dataset-specific&gt;?&lt;field&gt;=&lt;constraint&gt;"
> * The dataset-specific part isn't necessarily in that form
> * &lt;field&gt; must be a record field or a partition field. Anything else is ignored when constructing the view.
> * &lt;constraint&gt; makes more sense than "val1" because the latter implies that the URIs only support equality

Either way is fine with me. If you think examples are more clear than the pattern above, then let's go with that.