Feature, filter and SLD packages need @UML tags

Feature, filter and SLD packages need editorial work before we do any API change and/or before we bundle them in a GeoAPI 1.1 release:

• The class javadoc should contains an @version tag with the
  specification URL and version number. Example from CRS:

@author ISO 19111
@author <A HREF="http://www.opengis.org">OpenGIS® consortium</A>
@version <A HREF="http://www.opengis.org/docs/03-073r1.zip">Abstract specification 2.0</A>

• For each interfaces and each methods in org.opengis.feature, there is a choice:

• If the interface/method is derived from an OpenGIS specification,
  add a @UML annotation (commented out, but must still be present).
  E.g. from CRS:

/// @UML (identifier="usesDatum", obligation=MANDATORY)
Datum getDatum();

• Otherwise, if the interface/method is a GeoAPI addition, do not put any @UML annotation.

@UML annotations are an important part of GeoAPI. They are essential for helping us to track GeoAPI compliance to OGC standards. They are automatically parsed at building time, and used for automatic generation of the following page:

http://geoapi.sourceforge.net/snapshot/javadoc/org/opengis/doc-files/departures-list.html

Note that all feature, filter and sld interfaces are currently marked as non-standard because they don"t yet have @UML annotations.