Make MapView's setStyleJson public

[erf]

I would like to have setStyleJson as a public method in MapView, like so:

    public void setStyleJson(String json){
        mNativeMapView.setStyleJson(json);
    }

[1ec5]

For reference, on the iOS side, we removed -setStyleJSON: in #1299 but are definitely open to reintroducing granular styling in some form (#837).

[ljbade]

I'd much rather see #837 as the public API instead of this as setting the JSON directly is messy and I recall it causing issues a while ago.

@jfirebaugh Should we expose this to developers?

[jfirebaugh]

Yep, #837 covers what our plans are for public APIs in this area. @erf, let us know if for some reason your use case wouldn't be satisfied with that approach.

[erf]

@jfirebaugh #837 looks promising - has work on this begun for Android ?

[jfirebaugh]

No, we haven't started on it for any native platform yet.