RouteOptions parsing issuse

[LukasPaczos]

I was working with changes from #1118 today and noticed 2 issues so far:

I run into this NPE:

java.lang.NullPointerException: Attempt to invoke virtual method 'java.util.List com.mapbox.geojson.Point.coordinates()' on a null object reference
    at com.mapbox.geojson.BaseCoordinatesTypeAdapter.writePoint(BaseCoordinatesTypeAdapter.java:29)
    at com.mapbox.geojson.PointAsCoordinatesTypeAdapter.write(PointAsCoordinatesTypeAdapter.java:21)
    at com.mapbox.geojson.PointAsCoordinatesTypeAdapter.write(PointAsCoordinatesTypeAdapter.java:16)
    at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:69)
    at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.write(CollectionTypeAdapterFactory.java:97)
    at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.write(CollectionTypeAdapterFactory.java:61)
    at com.mapbox.api.directions.v5.models.AutoValue_RouteOptions$GsonTypeAdapter.write(AutoValue_RouteOptions.java:300)
    at com.mapbox.api.directions.v5.models.AutoValue_RouteOptions$GsonTypeAdapter.write(AutoValue_RouteOptions.java:41)
    at com.google.gson.Gson.toJson(Gson.java:704)
    at com.google.gson.Gson.toJson(Gson.java:683)
    at com.google.gson.Gson.toJson(Gson.java:638)
    at com.google.gson.Gson.toJson(Gson.java:618)
    at com.mapbox.api.directions.v5.models.DirectionsJsonObject.toJson(DirectionsJsonObject.java:30)

when initially provided waypoint_targets were ";lng,lat". That's because the serialization of Point doesn't expect nulls in BaseCoordinatesTypeAdapter.

Which brings us to issue number 2 - the newly created list of arguments do not accept nulls. An example can be the above crash, but also a way we need to provide other fields like bearingsList:

routeOptionsBuilder.bearingsList(listOf(listOf(angle, BEARING_TOLERANCE), listOf(null, null)))

We should instead be able to do:

routeOptionsBuilder.bearingsList(listOf(listOf(angle, BEARING_TOLERANCE), null))

but this will crash at bearings.size():

mapbox-java/services-directions/src/main/java/com/mapbox/api/directions/v5/MapboxDirections.java

Lines 681 to 686 in 123e7cd

	public Builder bearings(@NonNull List<List<Double>> bearings) {
	List<List<Double>> newBearings = new ArrayList<>();
	for (List<Double> bearing : bearings) {
	if (bearing.size() != 2) {
	throw new ServicesException("Bearing size should be 2.");
	}

which will throw and prevent us from making a request.

We'll need to iteratively iron out those conversion issues and cover them with tests, especially the JSON conversion.

@korshaknn would you be able to look into this?

/cc @mapbox/navigation-android if you see any other incompatibilities