Add ol.Observable for on, once, un, and unByKey methods
ol.Object extends ol.Observable
Merge pull request #1297 from tschaub/observable

Create ol.Observable.
Fix a typo - it's writers, not witers
Merge pull request #1336 from ahocevar/fix-writers-typo

Fix a typo - it's writers, not witers
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