Boundwidgetgroup mappings

This just changes the use of mappings from using multiple paramaters to using an object.
The old use of mappings was [here](https://github.com/siq/gloss/blob/master/src/widgets/boundwidgetgroup.js#L111) and [here](https://github.com/siq/gloss/blob/master/src/widgets/boundwidgetgroup.js#L230).

The only place this affects outside of gloss is in createinfoset.js in daft. There will be a similar pull request in daft for this so they can be merged at the same time.