BCBREAK: Refactor - Extract methods into BulkProcess[Behavior|Component]

- To make things DRYer, extract the common code into:
    * BulkProcessBehavior
    * BulkProcessComponent
- Some constants and variables have been deprecated.
- Node::actionsMapping has been removed
- A method introduced recently (Croogo::bulkProcessVars) has been moved
  and renamed to BulkProcessComponent::getRequestVars()
Refactor: Adapt Nodes plugin with new bulk processing code
Refactor: Adapt Blocks plugin with new bulk processing code
Refactor: Adapt Comments plugin with new bulk processing code
Refactor: Adapt Contacts plugin with new bulk processing code
Refactor: Adapt Menus plugin with new bulk processing code
Merge branch '2.0-bulk-refactor' into 2.0