I figured this was going to get flagged immediately, but I wanted to bring it up for discussion.  `baseMap` is an industry standard term.  It has a specific meaning, it's not just an `ImageryProvider`, it's the primary imagery provider that everything else is drawn on.  I'm okay with changing it, because you are correct that we don't use it anywhere else  (maybe we should), but `options.imageryProvider` doesn't seem specific enough.  I supposed we could use `options.imageryProvider` and have the description mention it's the base layer?