Message Content Rework

For now everything should look identical. However this moves to using a model for the content of the message and is intended to lay the foundation for improved message content representation, e.g. splitting up a text message in multiple sections and using different delegates for things like code and quotes.

src/linkpreviewer.cpp

@@ -13,8 +13,8 @@
 
 using namespace Quotient;
 
-LinkPreviewer::LinkPreviewer(const NeoChatRoom *room, const Quotient::RoomMessageEvent *event)
-    : QObject(nullptr)
+LinkPreviewer::LinkPreviewer(const NeoChatRoom *room, const Quotient::RoomMessageEvent *event, QObject *parent)
+    : QObject(parent)
     , m_currentRoom(room)
     , m_event(event)
     , m_loaded(false)