Separate out a base `MessageContentModel` that can be extended to get the component types from different places. This is used currently for `EventMessageContentModel` but will be used later as part of the rich chat bar.
All display text is now in the text component so it never needs special casing. This also cleans up some of the model parameters so more things come from attributes including location and file data (which was already a qvariantmap anyway).
Also cleaned up the itinerary and file enhancement views,
Title this adds a number of options for when messages should be automatically marked as read for the user to choose from.
{width=480 height=262}
Refactor TimelineView to make it more reliable and prepare for read marker choice. This is done by creating signalling from the mode when reset which can be used to move the scrollbar to the newest meassage.
Some of the spaghetti is also removed so there is no need for ChatBar and TimelineView to talk directly.
The code to mark messages as read if they are all visible after 10s has been removed infour of just marking as read on entry if all are visible. This is temporary until a follow up providing user options is finished (although it will be one of the options)
Most of the data in the objects will be empty, but at least a valid matrix id is provided.
This fixes missing data in some places in the UI (e.g., in HiddenDelegate)
