Add Feed and FeedItem

Also:
* _finalizeErase in Zotero.DataObject is now inheritable
* Call _initErase before starting a DB transaction
* removes Zotero.Libraries.add and Zotero.Libraries.remove (doesn't seem like this is used any more)

components/zotero-service.js

@@ -61,6 +61,8 @@ const xpcomFilesLocal = [
 	'attachments',
 	'cite',
 	'cookieSandbox',
+	'data/library',
+	'data/libraries',
 	'data/dataObject',
 	'data/dataObjects',
 	'data/dataObjectUtilities',
@@ -70,11 +72,14 @@ const xpcomFilesLocal = [
 	'data/items',
 	'data/collection',
 	'data/collections',
+	'data/feedItem',
+	'data/feedItems',
+	'data/feed',
+	'data/feeds',
 	'data/creators',
 	'data/group',
 	'data/groups',
 	'data/itemFields',
-	'data/libraries',
 	'data/relations',
 	'data/tags',
 	'db',