Fix for #366 (#417)

The 2.2.0 does not fixes my issue, this is. While the generators are made prototypes (non singletons), the core components (managers) are still singletons, and the fact they inject Map<String, Generator> still makes generators singletons...

Author: cstamas

modello-core/src/main/java/org/codehaus/modello/core/DefaultGeneratorPluginManager.java

@@ -24,7 +24,6 @@
 
 import javax.inject.Inject;
 import javax.inject.Named;
-import javax.inject.Singleton;
 
 import java.util.Map;
 
@@ -36,7 +35,6 @@
  * @author <a href="mailto:trygvis@inamo.no">Trygve Laugst&oslash;l</a>
  */
 @Named
-@Singleton
 public class DefaultGeneratorPluginManager extends AbstractPluginManager<ModelloGenerator>
         implements GeneratorPluginManager {
 

modello-core/src/main/java/org/codehaus/modello/core/DefaultMetadataPluginManager.java

@@ -24,7 +24,6 @@
 
 import javax.inject.Inject;
 import javax.inject.Named;
-import javax.inject.Singleton;
 
 import java.util.Map;
 
@@ -36,7 +35,6 @@
  * @author <a href="mailto:trygvis@inamo.no">Trygve Laugst&oslash;l</a>
  */
 @Named
-@Singleton
 public class DefaultMetadataPluginManager extends AbstractPluginManager<MetadataPlugin>
         implements MetadataPluginManager {
 

modello-core/src/main/java/org/codehaus/modello/core/DefaultModelloCore.java

@@ -24,7 +24,6 @@
 
 import javax.inject.Inject;
 import javax.inject.Named;
-import javax.inject.Singleton;
 
 import java.io.File;
 import java.io.IOException;
@@ -60,7 +59,6 @@
  * @author <a href="mailto:evenisse@codehaus.org">Emmanuel Venisse</a>
  */
 @Named
-@Singleton
 public class DefaultModelloCore extends AbstractModelloCore {
 
     @Inject