DefaultModuleService: change persisting of items

Disable the persisting of a ModuleItems if an initialize() method is set
and is not empty. This way, initialize() can overwrite the value of a
ModuleItem even if persist=true is assumed implicitly.

See:
* imagej/imagej-legacy#137 (comment)

Author: stelfrich

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

@@ -291,6 +291,9 @@ public ModuleItem<?> getSingleOutput(Module module, Collection<Class<?>> types)
 	public <T> void save(final ModuleItem<T> item, final T value) {
 		if (!item.isPersisted()) return;
 
+		// NB: Do not persist values which are computed via an initializer.
+		if (item.getInitializer() != null && !item.getInitializer().isEmpty()) 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,