WrapperService: fix create method return type

It will -- and should -- always return an instance of PT specifically.
That is the point of the generic typing on plugin type: to define and
guarantee use of that specific type. Not just "WrapperPlugin<D>".

This change will eliminate a few hacky casts downstream, too.

Author: ctrueden

src/main/java/org/scijava/plugin/AbstractWrapperService.java

@@ -50,16 +50,13 @@ public abstract class AbstractWrapperService<DT, PT extends WrapperPlugin<DT>>
 	// -- WrapperService methods --
 
 	@Override
-	public <D extends DT> WrapperPlugin<D> create(final D data) {
+	public <D extends DT> PT create(final D data) {
 		final PT instance = wrap(data);
 		if (instance == null) {
 			throw new IllegalArgumentException("No compatible " +
 				getPluginType().getSimpleName() + " for data object: " + data);
 		}
-		@SuppressWarnings("unchecked")
-		final WrapperPlugin<D> typedInstance = (WrapperPlugin<D>) instance;
-		typedInstance.set(data);
-		return typedInstance;
+		return instance;
 	}
 
 	// -- Service methods --

src/main/java/org/scijava/plugin/WrapperService.java

@@ -62,6 +62,6 @@ public interface WrapperService<DT, PT extends WrapperPlugin<DT>> extends
 	 * @throws IllegalArgumentException if the data is not compatible with any
 	 *           available plugin.
 	 */
-	<D extends DT> WrapperPlugin<D> create(D data);
+	<D extends DT> PT create(D data);
 
 }