New methods: Croogo.Wysiwyg.isDirty()|resetDirty()
New method Admin.protectForms()

Protect accidental page refresh causing data loss:

- To protect a form, add 'protected-form' in the class attribute.
- To whitelist elements, add 'data-ignore-elements' containing its selector
Protect some forms from accidental data loss

Closes #410
Merge branch '2.0-dirty-bit' into 2.0
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