Now that we have FeatureId support (see #733), we can add this back to the
GML parsers (v2 and v3). Also add write support for FeatureId in KML, read
support was already added by @fredj
This is a follow-up for https://github.com/openlayers/ol3/pull/711
for the GML parser. Also use goog.array.map instead of map as was
pointed out by @twpayne on the WKT review and update the example data
to use all US states as pointed out by @tschaub on the Google hangout.
This adds a parser (read/write) for GML v2 and v3. GML v3 is limited to the
simple features profile of GML 3.1.1, just like OpenLayers 2 was. This will
be the basis for the WFS parser, but it only makes sense to continue this work
once feature modification (insert, update, delete) is in place in ol3. So the
WFS parser will be another pull request.
