upgrade to maven 3.0.3 (will prevent issue when pom parsing phase : http://jira.codehaus.org/browse/MNG-4963)

Revert "adding something to DescriptorExtensionList should cause addition to ExtensionList of Descriptors as well."

This reverts commit 04d64fd4.

By the time MavenModuleSetBuild.notifyModuleBuild() is called, we need the processing on one module to be completed.

adding something to DescriptorExtensionList should cause addition to ExtensionList of Descriptors as well.

To make views reusable elsewhere, removing "Manage Jenkins" from View and moving the logic to the top-level Hudson class.

Added ViewGroup.getItemGroup() so that views can be used with ItemGroups in general, not just with Hudson.

extracted the commonality into ViewGroupMixIn, much like we have ItemGroupMixIn. This makes reuse in plugins easier, too.