Restructured TODO, and added some new stuff

Signed-off-by: Gergely POLONKAI <polesz@w00d5t0ck.info>

TODO

@@ -1,105 +1,106 @@
 * book creation
-
 * event creation
-
 * "sticky" news flag
-
+* songs
 * news editor for administrators
-
 * PDF header fix
-
 * draft flag for Document and Article: only writer and administrators see it
     from the Document/Article list, in preview mode
-
 * full Document/Article list for administrators
-
 * polls
-
 * chat
-
 * Users' favourite forum topics
-
 * article categories
-
 * blog
-
 * site-based theme for ckeditor (both ui and the editor)
 
+Song
+    id
+    title
+    createdBy
+    createdAt
+    SongVersion[]
+        id
+        createdBy
+        createdAt
+        content
+
+News
+    lead
+
 Poll
-	id
-	createdAt
-	createdBy
-	updatedAt
-	updatedBy
-	updateReason
-	endTime (timestamp/date?)
-	answers (ArrayCollection of PollAnswers)
-	text
-	anyoneCanAddAnswers
-	multiselect
-	voters (is it really required?)
-PollAnswer
-	id
-	createdAt
-	createdBy
-	updatedAt
-	updatedBy
-	updateReason
-	voters
-	poll (back-reference to Poll)
-	text
+    id
+    createdAt
+    createdBy
+    updatedAt
+    updatedBy
+    updateReason
+    endTime (timestamp/date?)
+    anyoneCanAddAnswers
+    question
+    multiselect
+    voters
+    PollAnswer[]
+        id
+        createdAt
+        createdBy
+        updatedAt
+        updatedBy
+        updateReason
+        voters
+        text
 
 UserForumViewed
-	User
-	ForumTopic
-	timestamp of last visit
+    User
+    ForumTopic
+    timestamp of last visit
 
 BlogPost
-	id
-	title
-	slug
-	timestamp
-	lead (?)
-	text
-	poster
-	public
+    id
+    title
+    slug
+    timestamp
+    lead (?)
+    text
+    poster
+    public
 
 ForumTopicGroup
-	visible
-	locked
+    visible
+    locked
 
 ForumTopic
-	roles who can access it
-	visible
-	locked
+    roles who can access it
+    visible
+    locked
 
 ForumPost
-	last edited by
-	last edited timestamp
-	last edit reason
-	edit count
+    last edited by
+    last edited timestamp
+    last edit reason
+    edit count
 
 Event
-	last edited by
-	last edited timestamp
-	last edit reason
-	location
-	commentable
+    last edited by
+    last edited timestamp
+    last edit reason
+    location
+    commentable
 
 PrivateChatMessage
-	id
-	from user
-	to user
-	timestamp
+    id
+    from user
+    to user
+    timestamp
 
 GroupChatMessage
-	id
-	from user
-	to group
-	timestamp
+    id
+    from user
+    to group
+    timestamp
 
 PublicChatMessage
-	id
-	from user
-	to channel (ChatChannel class with id and name fields)
-	timestamp
+    id
+    from user
+    to channel (ChatChannel class with id and name fields)
+    timestamp