contentdatastore: fix events system
Moving datastore classes from impl package into org.geotools.data.wfs.
Merge pull request #491 from jdeolive/wfs-ng-pluggable

Moving WFSDataStoreFactory to org.geotools.data.wfs package.
GEOT-4833
Merge pull request #496 from geosolutions-it/upstream

GEOT-4833, GeoTiffReader sometimes leaves uncloseable files
Merge pull request #492 from NielsCharlier/events

contentdatastore: fix events system
[GEOT-4843] Add support for circular geometries (object model)
[GEOT-4843] Add support for circular geometries (WktReader2 and geometry converter integration)
[GEOT-4843] Add support for circular geometries (rendering optimizations and tests)