Move the reaction delegate into the bubble so it can be instantiated by the Content model. This aims to make sure we only instantiate it when needed rather than for every event. You can now hover the event to show the ReactionComponent with a button to add a reaction if none are currently present
Added bonus ReactionModel no longer needs an event pointer, the event ID is enough to get reaction from the room so things are less likely to blow up.
The focus here is to make threads use the standard message content system rather than having a special implementation.
To achieve this the threadroot content model will now get a thread body component which will visualise the thread model with all the other messages. The latest message in the thread will then just ask for the thread root content model and show that.
Note: in order to stop a cyclical dependency with MessageComponentChooser and new base version has been added which is just missing ThreadBodyComponent and and the main version is now inherited from that with ThreadBodyComponent added.
