Schema per rz-doc - each doc can be modified to allow only a subset of the node types defined in the instance

[alon]

Add a list of limiting node types per doc.

Requirements / Implementation:

• client: settings dialog accessible from doc name (with settings icon) including a checkbox per node type, able to change.
• API point: /rz/<doc-id>/settings/submit (or just settings and POST, check REST common measures for this - don't want to have to change this later
• server implementation: store on the RZ_DOC node that already exists settings:allowed_nodes:List NodeType
• server: when a new type per node is set check for limit (changes in TBD places)
• server clone end point: send the settings, which will include the allowed_nodes list
• client: limit node types presented to the list received.

Things we will not do:

• remove no longer complying nodes automatically for the user.

Things to do later:

• allow only certain users to change these settings

[Garbash]

I'd argue we shouldn't allow anyone to mess with the setting from the get-go. My proposal:

• Setting dialogue will only be available to users defined as "admins" of the doc, or "super-admins" of the instance.