Improve order of preprocessor plugins

The validity check should come extremely early.
After that, the Gateway and Service population should happen ASAP.
Only then should we consider others such as single typed inputs.

Without this change, it was possible for parameter validator
methods to fire before services were populated.

Author: ctrueden

src/main/java/org/scijava/module/process/GatewayPreprocessor.java

@@ -52,8 +52,8 @@
  * 
  * @author Curtis Rueden
  */
-@Plugin(type = PreprocessorPlugin.class,
-	priority = Priority.VERY_HIGH_PRIORITY)
+@Plugin(type = PreprocessorPlugin.class, //
+	priority = 2 * Priority.VERY_HIGH_PRIORITY)
 public class GatewayPreprocessor extends AbstractPreprocessorPlugin {
 
 	@Parameter

src/main/java/org/scijava/module/process/ServicePreprocessor.java

@@ -61,8 +61,8 @@
  * 
  * @author Curtis Rueden
  */
-@Plugin(type = PreprocessorPlugin.class,
-	priority = Priority.VERY_HIGH_PRIORITY)
+@Plugin(type = PreprocessorPlugin.class, //
+	priority = 2 * Priority.VERY_HIGH_PRIORITY)
 public class ServicePreprocessor extends AbstractPreprocessorPlugin {
 
 	// -- ModuleProcessor methods --

src/main/java/org/scijava/module/process/ValidityPreprocessor.java

@@ -44,7 +44,7 @@
  * @author Curtis Rueden
  */
 @Plugin(type = PreprocessorPlugin.class,
-	priority = Priority.VERY_HIGH_PRIORITY + 1)
+	priority = 3 * Priority.VERY_HIGH_PRIORITY)
 public class ValidityPreprocessor extends AbstractPreprocessorPlugin {
 
 	// -- ModuleProcessor methods --