Add support for Capability "node-update"

[sammefford]

A new capability has been added in support of element level security. It's called "node-update". We need to add it to DocumentMetadataHandle.Capability. I'm thinking we'll call it NODE_UPDATE.

[grechaw]

👍

[sammefford]

Ajit, I don't have a unit test that validates this as working through to the rest layer. Could you make a regression test for that?

[sammefford]

For QA we need to write a document with metadata that says a permission gives a specific role the node-update capability. Also we should read the metadata for the document and see that it has that permission with that roles assigned node-update capability.