fix(dataLayer): only update those data options which were changed

[vincentsels]

Fixes #1099 and probably similar issues, where updating the data of a data layer causes all data options to be cleared, because they are not passed along, hence null is passed in as a value to setControlPosition etc, instead of the actual values.

Note that this will obviously prevent actually clearing these 'data options' by setting them to null, but fixing this would require further refactoring.

[lazarljubenovic]

With a single function like this, the only way (that I'm aware of) to differentiate between "leave this option as it was" and "clear this option" is to make use of difference between undefined and null.

So maybe it would be better to use if (xxx !== undefined) (notice the usage of strict comparison)?

But we should also check with how Google's JS API for Maps handles this and try to be as close as possible with it.

[sebholstein]

I think the only way to make this more efficient would be to use the ngOnChanges callback and differenciate between the provided changes.

Otherwise, it would not be possible to change a certain setting to undefined or null.

So I'm closing this - feel free to open a new PR that covers a smarter update mechanism with the ngOnChanges callback. Thanks for your time 👍