Ability to tweak settings on a per node basis

Problem/Motivation

Some nodes require different configuration options than the content type level configuration. For example, we don't want to keep any revisions in general for the 'page' content type , but there are a couple of frequently updated pages that we want to keep a weeks worth of revisions.

Proposed resolution

Allow for per node revision delete configuration.

Remaining tasks

• Build the form on nodes that are configured to remove revisions.
• Override the default logic to determine candidates using the per-node configuration, if it exists.

User interface changes

Add form elements to the Revisions tab at the bottom of the node edit page.

API changes

None.

Data model changes

None, will store per-node data in variables table.