bug(web): API function `util.setOption` is incomplete.

Presently, the `util.setOption` API function only changes the raw value of the option being set. Literally zero effort is undertaken to ensure that the newly-set option is actually active within the KeymanWeb system or makes logical sense for the system.

Known problems resulting from this:

- It is impossible to change attachment type after the page has initialized, despite being able to make a `setOption('attachType', 'auto')` or `setOption('attachType', 'manual')` call.
- It is impossible to change user-interface type for desktop devices after initialization, despite being able to make calls like `setOption('ui', 'toggle')`.
- It is unclear what effect changing some of the path-oriented options would have at runtime, but some of these should likely be blocked and/or produce warnings.