Proper namespace and sub-parser management

Instead of setting a dummy namespace, we can have setter methods
for the featureNS property to propagate them to sub-parsers. The
srsName is also a property which needs to be propagated to
sub-parsers.
Merge pull request #1337 from ahocevar/no-foo

Proper namespace and sub-parser management in OGC parsers
Merge remote-tracking branch 'openlayers/master' into vector-api
Make ol.geom.Geometry inherit from ol.Observable
Render simplified geometries in replay mode
Add initial ol.geom.simplify
Add ol.geom.simplify.douglasPeukers
Add ol.geom.simplify.douglasPeukerss
Add ol.geom.Geometry#getSimplifiedGeometry
Add ol.geom.LineString#getSimplifiedGeometryInternal
Add ol.geom.Polygon#getSimplifiedGeometryInternal
Add ol.geom.MultiLineString#getSimplifiedGeometryInternal
Add ol.geom.MultiPolygon#getSimplifiedGeometryInternal