More readable, eliminated some vestigial properties in DocumentsListController.
Preparing to try a different method for setting a document to be ubiquitous:
 Renamed NPCloudDocURLKey -> NPDocCloudSyncURLKey;
Added NPSuccessCallbackKey & NPFailureCallbackKey to the record, for handier callbacks.
This version (and the previous) demonstrates iCloud syncing of UIManagedDocuments, but I noticed something odd. Here, on [+]
    ( calls -(IBAction)addDocument:(id)sender and -(void)establishDocument: (UIManagedDocument*)document),
the app:
  creates a document,
  initializes its object graph,
  closes it,
  sets it ubiquitous, then
  opens it.
It works (much of the time).
But, apparently, the operations of -setUbiquitous and -openWithCompletionHandler: interleave.
See this passage from the creating device’s debugger log:
	2014-05-14 15:43:39.688 multidocument[1556:60b] Saved new document for creating
	2014-05-14 15:43:39.688 multidocument[1556:60b] Creating a new text entry
	2014-05-14 15:43:39.743 multidocument[1556:60b] Creating a new model version
	2014-05-14 15:43:40.232 multidocument[1556:60b] Closed new document: Success
	2014-05-14 15:43:40.238 multidocument[1556:60b] -setUbiquitous: async queue did dispatch
	2014-05-14 15:43:40.238 multidocument[1556:3507]  in dispatch_async  -setUbiquitous:error:
	2014-05-14 15:43:40.238 multidocument[1556:60b] openWithCompletionHandler: start
	2014-05-14 15:43:40.679 multidocument[1556:3507]  in dispatch_async -setUbiquitous:error: SUCCESS
	2014-05-14 15:43:40.753 multidocument[1556:3507]  in dispatch_async startDownloadingUbiquitousItemAtURL SUCCESS
	2014-05-14 15:43:40.754 multidocument[1556:3507]  in dispatch_async -setUbiquitous:error: end
	2014-05-14 15:43:41.238 multidocument[1556:60b] iPhone: -actuallyReloadTableView:
	2014-05-14 15:43:41.270 multidocument[1556:4903] -[PFUbiquitySwitchboardEntryMetadata setUseLocalStorage:](771): CoreData: Ubiquity:  mobile~361E0DEC-1700-4F1F-A19F-436DC04F31D6:1A4923F9-A057-4D1B-8818-4C17B1C7CBD2
Using local storage: 1
	2014-05-14 15:43:41.403 multidocument[1556:60b] openWithCompletionHandler: succeeded. Opened the created file for reading.

I tried a different way to make the document ubiquitous, following Zarra:
Core Data, 2nd Edition
 Data Storage and Management for iOS, OS X, and iCloud
 by Marcus S. Zarra
 ISBN-13: 978-1-937785-08-6
 Chapter 6. Using iCloud • Page 108
I failed to make it work, but I’m leaving --(void)addCloudPersistentStore: (NSDictionary*)record in the source anyway, so I can show what I tried.
Committing after abandoning all hope on:
[1] adding a persistent store with cloud-style options to a document with local-style options.
[2] setting ubiquitous, then opening the document using its cloud url (opens successfully but crashes immediately).
Conclusion: I have found no way around what I see to be a race condition between -setUbiquitous: and -openWithCompletionHandler:.
Just discovered (!) iCloud and Core Data - Syncing Data - objc.io issue #10
http://www.objc.io/issue-10/icloud-core-data.html

I modified the observers to follow (neglecting for this commit  -migrateiCloudStoreToLocalStore and “To set up your persistent store for iCloud, there are a few options you need to be aware of to pass when calling addPersistentStoreWithType:configuration:URL:options:error: or migratePersistentStore:toURL:options:withType:error::”

This version works but badly. It often crashes on a Core Data error. But I was able to demonstrate a sustained ping exchange.

Next: -addPersistentStoreWithType: to move the document to iCloud.
I’m suddenly getting errors of this form:
2014-05-16 13:18:46.627 multidocument[2351:320f] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'I/O error for database at /var/mobile/Applications/BC35B46A-A570-413C-A4EA-9783C5045043/Documents/46665C67-B6D7-4176-B536-E306596356E1/TestDoc1/StoreContent.nosync/CoreDataUbiquitySupport/mobile~7D0A09B5-B998-4750-90C2-3AE2C27A35B8/46665C67-B6D7-4176-B536-E306596356E1/E5F755DF-60A1-4522-B1DB-D68F268B257E/store/persistentStore.  SQLite error code:1802, 'not an error''
*** First throw call stack:
(0x2f711f0b 0x39ea8ce7 0x2f45ea43 0x2f45e101 0x2f51858f 0x2f519491 0x2f49d80b 0x2f496669 0x2f5c426d 0x2f5c2e73 0x2f58f68b 0x3a391d53 0x3a396cbd 0x3a393c6f 0x3a3975f1 0x3a3978dd 0x3a4c2c17 0x3a4c2adc)
libc++abi.dylib: terminating with uncaught exception of type _NSCoreDataException

I have good luck (low statistics) avoiding those errors with this workaround:
[1] touch the [+] (add document) button in the root view
[2] wait several seconds before selecting the new row to see the new document’s object graph in the detail view.
I updated the documentation to highlight this.
Failed to find a better way to -setUbiquitous

It seems that the only way to set a document ubiquitous is to dispatch
[NSFileManger setUbiquitous…] asynchronously, and immediately call
-[UIDocument openWithCompletionHandler:], setting up what would appear
to be a race condition that happens to yield the desired result. I
tried adding a persistent store with cloud-specific options, but that
failed.