info view: better display of prerequisites

[oliver-sanders]

The info view currently displays task prerequisites in much the same way as the cylc show command.

With the power of the web browser we can enhance this quite a lot. Ideas:

• Query the state and outputs of all prerequisite tasks:
  • This requires offline task data to be available at the UIS.
  • Note, you can't just rely on this data being in the central data store, it often wont be (hence the offline data requirement).
• Display the task icon of prerequisite tasks:
  • This would make it easier to access the prerequisite tasks (e.g. set required outputs directly from the info view).
  • It would also make it easier to tell if any prereqs are failed or held.
• Display the prerequisite conditions in a fancier way:
  • The "taskAlias" approach is clunky.
  • E.G, we could format the prerequisites similar to how we format completion conditions.