Add 'hide mastered' checkbox to job assignments window

[yoakenashi]

When you have an absurd number of duplicants like I regularly do, it becomes a little cumbersome to identify the job a duplicant should be assigned.

If many of the duplicants have mastered a job, then selecting the "Vacant Position" drop down box shows many of the duplicants with crowns. It's difficult to sift through these to identify who still needs to be trained in this job.

Also, if your duplicants have mastered many jobs, then selecting the "No Job" drop down box shows many jobs mastered. It's difficult to identify what jobs still need to be mastered.

A checkbox at the top of this window to "Hide Mastered Jobs" would hide all those jobs a particular duplicant has mastered, and only show those jobs that duplicant hasn't mastered.

I'm super glad Klei added the crowns to begin with and told myself I wouldn't ask for additional changes to the job assignments window, but - I can't help myself

Cheers Klei