Validate TextSearchRequest without query if type is set

[danoscarmike]

Updated logic in validateRequest method of TextSearchRequest class

Fixes #564

[domesticmouse]

Please add a test 😉

[danoscarmike]

I actually started to write one but then realized there is no obvious existing test class file in which to put it. Happy to create one but I'm wondering if instead we should overload the PlacesApi.textSearchQuery method with something like:

public static TextSearchRequest textSearchQuery(GeoApiContext context, PlaceType type) {
    TextSearchRequest request = new TextSearchRequest(context);
    request.type(type);
    return request;
}

Could easily extend existing tests then. WDYT?

[domesticmouse]

I think I'll think about this after I/O =)