ConvertService: return collection

Instead of returning a List of input candidates, we can generalize to
Collection.

Author: hinerm

src/main/java/org/scijava/convert/ConvertService.java

@@ -32,7 +32,7 @@
 package org.scijava.convert;
 
 import java.lang.reflect.Type;
-import java.util.List;
+import java.util.Collection;
 
 import org.scijava.plugin.HandlerService;
 
@@ -103,5 +103,5 @@ public interface ConvertService extends
 	 */
 	boolean supports(Class<?> src, Type dest);
 
-	List<Object> getCompatibleInputs(Class<?> dest);
+	Collection<Object> getCompatibleInputs(Class<?> dest);
 }

src/main/java/org/scijava/convert/DefaultConvertService.java

@@ -33,8 +33,8 @@
 
 import java.lang.reflect.Type;
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.HashSet;
-import java.util.List;
 import java.util.Set;
 
 import org.scijava.plugin.Plugin;
@@ -102,7 +102,7 @@ public boolean supports(final Class<?> src, final Type dest) {
 	}
 
 	@Override
-	public List<Object> getCompatibleInputs(Class<?> dest) {
+	public Collection<Object> getCompatibleInputs(Class<?> dest) {
 		Set<Object> objects = new HashSet<Object>();
 
 		for (final Converter c : getInstances()) {

src/main/java/org/scijava/widget/AbstractInputHarvester.java

@@ -150,7 +150,8 @@ private <T> WidgetModel addInput(final InputPanel<P, W> inputPanel,
 	@SuppressWarnings("unchecked")
 	private List<?> getObjects(final Class<?> type) {
 		@SuppressWarnings("rawtypes")
-		List compatibleInputs = convertService.getCompatibleInputs(type);
+		List compatibleInputs =
+			new ArrayList(convertService.getCompatibleInputs(type));
 		compatibleInputs.addAll(objectService.getObjects(type));
 		return compatibleInputs;
 	}