Ensure map options are respected after free-drawing polygons

Resolves #952.

It's a bug fix, because there was already code in there to revert the map options after drawing, but it wasn't quite working the right way.

Changes:

* Use `@oldOptions = map.getOptions().options` instead of `@oldOptions = map.getOptions()`.
* Use `@map.setOptions _.defaults @oldOptions, enabledMapOptions` instead of `@map.setOptions _.extend @oldOptions, defaultOptions`.
@nmccready Before we can merge, I need to change `ctrl.getScope().options` to `map.getOptions().options`. So can I pass `ctrl` into DrawFreeHandChildModel here? Or pass in `ctrl.getScope()`? Whatever you are happy with.