DefaultModuleService: do not persist default value

This makes iterative script development slightly more convenient.

Thanks to Leon Yang for the idea.

Author: ctrueden

src/main/java/org/scijava/module/DefaultModuleService.java

@@ -60,6 +60,7 @@
 import org.scijava.service.Service;
 import org.scijava.thread.ThreadService;
 import org.scijava.util.ClassUtils;
+import org.scijava.util.MiscUtils;
 
 /**
  * Default service for keeping track of and executing available modules.
@@ -266,6 +267,13 @@ public <T> ModuleItem<T> getSingleOutput(final Module module,
 	public <T> void save(final ModuleItem<T> item, final T value) {
 		if (!item.isPersisted()) return;
 
+		if (MiscUtils.equal(item.getDefaultValue(), value)) {
+			// NB: Do not persist the value if it is the default.
+			// This is nice if the default value might change later,
+			// such as when iteratively developing a script.
+			return;
+		}
+
 		final String sValue = value == null ? "" : value.toString();
 
 		// do not persist if object cannot be converted back from a string