In other widgets, I reorganized code like this to use local variables throughout all this HTML code, and then assign all the properties in one block after calling `applyBindings`.  I think that makes it easier to see the actual properties instead of having everything all jumbled together.  It also makes it easier to see which properties are actually needed, e.g. in this case, `this._titleElement` is never used.  Compare to `BaseLayerPicker`