Give specific task info if scrolling through job booklet

[Banjobeni]

For complex loading/unloading jobs, specific car groups need taken from or to different tracks. The player can flip pages through an (accepted) job booklet. If we could know which page the player is on, and which tasks this page corresponds to, we could display info only for that task and that group of cars.

There are two problems to solve here. Firstly, getting the required info about the pages of a JobBooklet and the currently displayed page. Secondly, determining task data that gives us info on what to display.

We would want to indicate if the currently flipped-to task is finished. The problem here is that there does not seem to be a direct mapping between a Page and a DV.Logic.Job.Task. In order to know if a page task is finished, we may need to have some heuristics for that mapping.

Previously discussed in #4.

[Cappycot]

I checked the code that "prints" the job booklet when a job is accepted/loaded and it appears to be hard-coded at the time of writing this comment since there are only four different types of jobs (shunting load, shunting unload, transport, and empty transport).

I'm probably going to try mapping dispatch hints to each of these pages next week.

[Banjobeni]

A mapping from page to DV.Logic.Job.Task (i.e. not directly to a dispatch hint) would allow us to indicate that the task for the current page is completed.