Relations overhaul (requires new DB upgrade from 4.0)

Relations are now properties of collections and items rather than
first-class objects, stored in separate collectionRelations and
itemRelations tables with ids for subjects, with foreign keys to the
associated data objects.

Related items now use dc:relation relations rather than a separate table
(among other reasons, because API syncing won't necessarily sync both
items at the same time, so they can't be stored by id).

The UI assigns related-item relations bidirectionally, and checks for
related-item and linked-object relations are done unidirectionally by
default.

dc:isReplacedBy is now dc:replaces, so that the subject is an existing
object, and the predicate is now named
Zotero.Attachments.replacedItemPredicate.

Some additional work is still needed, notably around following
replaced-item relations, and migration needs to be tested more fully,
but this seems to mostly work.

test/tests/relatedboxTest.js

@@ -0,0 +1,103 @@
+"use strict";
+
+describe("Related Box", function () {
+	var win, doc, itemsView;
+	
+	before(function* () {
+		win = yield loadZoteroPane();
+		doc = win.document;
+		itemsView = win.ZoteroPane.itemsView;
+	});
+	after(function () {
+		win.close();
+	})
+	
+	describe("Add button", function () {
+		it("should add a related item", function* () {
+			var item1 = yield createDataObject('item');
+			var item2 = yield createDataObject('item');
+			
+			// Select the Related pane
+			var tabbox = doc.getElementById('zotero-view-tabbox');
+			tabbox.selectedIndex = 3;
+			var relatedbox = doc.getElementById('zotero-editpane-related');
+			assert.lengthOf(relatedbox.id('relatedRows').childNodes, 0);
+			
+			// Click the Add button to open the Select Items dialog
+			setTimeout(function () {
+				relatedbox.id('addButton').click();
+			});
+			var selectWin = yield waitForWindow('chrome://zotero/content/selectItemsDialog.xul');
+			// wrappedJSObject isn't working on zotero-collections-tree for some reason, so
+			// just wait for the items tree to be created and select it directly
+			do {
+				var view = selectWin.document.getElementById('zotero-items-tree').view.wrappedJSObject;
+				yield Zotero.Promise.delay(50);
+			}
+			while (!view);
+			var deferred = Zotero.Promise.defer();
+			view.addEventListener('load', () => deferred.resolve());
+			yield deferred.promise;
+			
+			// Select the other item
+			for (let i = 0; i < view.rowCount; i++) {
+				if (view.getRow(i).ref.id == item1.id) {
+					view.selection.select(i);
+				}
+			}
+			selectWin.document.documentElement.acceptDialog();
+			
+			// Wait for relations list to populate
+			do {
+				yield Zotero.Promise.delay(50);
+			}
+			while (!relatedbox.id('relatedRows').childNodes.length);
+			
+			assert.lengthOf(relatedbox.id('relatedRows').childNodes, 1);
+			
+			var items = item1.relatedItems;
+			assert.lengthOf(items, 1);
+			assert.equal(items[0], item2.key);
+			
+			// Relation should be assigned bidirectionally
+			var items = item2.relatedItems;
+			assert.lengthOf(items, 1);
+			assert.equal(items[0], item1.key);
+		})
+	})
+	
+	describe("Remove button", function () {
+		it("should remove a related item", function* () {
+			var item1 = yield createDataObject('item');
+			var item2 = yield createDataObject('item');
+			
+			yield item1.loadRelations();
+			item1.addRelatedItem(item2);
+			yield item1.save();
+			yield item2.loadRelations();
+			item2.addRelatedItem(item1);
+			yield item2.save();
+			
+			// Select the Related pane
+			var tabbox = doc.getElementById('zotero-view-tabbox');
+			tabbox.selectedIndex = 3;
+			var relatedbox = doc.getElementById('zotero-editpane-related');
+			
+			// Wait for relations list to populate
+			do {
+				yield Zotero.Promise.delay(50);
+			}
+			while (!relatedbox.id('relatedRows').childNodes.length);
+			
+			doc.getAnonymousNodes(relatedbox)[0]
+				.getElementsByAttribute('value', '-')[0]
+				.click();
+			
+			// Wait for relations list to clear
+			do {
+				yield Zotero.Promise.delay(50);
+			}
+			while (relatedbox.id('relatedRows').childNodes.length);
+		})
+	})
+})