Globe default value

Before: new GlobeCoordinateValue( $latLang, $precision ) was possible but
new GlobeCoordinateValue( $latLang, $precision, null ) failed. Doesn't make
much sense if you think about, especially in terms of deserialization.

After: Both calls use the default value.

Bug: 66632
Merge pull request #13 from DataValues/globe-null

Globe default value