Window to preselect job at level 0

[uecasm]

Changes proposed in this pull request:

• Adds a window that appears instead of an error message if you click Manage Workers on a level 0 hut. This allows you to pre-select the job(s) that will work there once upgraded to level 1 -- most importantly, preventing the "wrong" job being hired before you have a chance to change it, when the colony is set to automatic hiring. This means there's less need to set the colony to manual hiring.
  • The window shows the job name and tooltip from the "real" Manage Workers screen.
    
    • Clicking a job name sets that job to Colony Default and all other jobs to Manual.
    • Clicking Nobody sets all jobs to Manual.
    • Clicking Anybody sets all jobs to Colony Default.
  • A simplified version appears when there's only one possible job:
    
    • This lets you set that job to either Manual or Colony Default.
  • There's no difference between jobs that only let you hire one type vs. jobs that allow multiple (if we want to make that distinction, the "anybody" button text would probably be the only thing that changed, but the current one seems sufficient).
    
• It also appears for the warehouse and quarry assignment at level 0 instead of just showing an error.

[x] Yes I tested this before submitting it.
[ ] I also did a multiplayer test.

Review please (could port)

This was originally more complicated -- it would auto-open on placing the hut (either normally or with paste), and only if there were multiple jobs -- but that required network messages (so would have been harder to port), required some additional state transfer and persistence, and overall just seemed messier. This approach seems nicer.