Move all task options to the viewer

[alexandermendes]

We currently translate a list of task configuration options into an arbitrary task object that is then passed around within the viewer. This somewhat breaks the reactivity of Vue as we can't then easily reconfigure the task, for example, to change a highlighted region or update a form field from outside the module.

One of the advantages to storing task objects initially was to provide the browse functionality but we might need to rethink this...

[alexandermendes]

This was triggered as I start to look at adding the review mode, which will take a list of annotations and present them to the user for review. However, we may need to change these displayed annotations depending on user input and here we realise that reactivity is broken. We either need to regenerate the task or go through an unnecessarily complex process of matching up IDs.

In general, it feels like adding a task configuration forces a particular structure on the user that we don't really need. The browse functionality could still be implemented by the client be responding to clicks of the next/previous buttons.

[alexandermendes]

Another advantage of passing in a list of tasks was so that we could preload the tile sources, however, as we're not actually doing this at the moment it's not functionality that we lose. It could still be something to consider at a later date.