[RFC] Overhaul training

[lewri]

Fixes #1458
Fixes #2262

Describe what the proposed change does

• Overhauls the training system to be a bit more akin to TH (based on dissection in 1458). It also means training is more reactive to several factors (TODOs in code).
• The math.rand modulo function was not incorporated, as it caused a lot of groundhog day scenarios with docs nearer consultant level
• Large explanation comments currently left in, to be moved to the Wiki, and shortened in the lua file, if plan to merge.

For award values following this PR: (before PR general skill was 0.0035 regardless of factors)

1-3 trainees with 1 consultant (no specialities): 0.004 per day (0.03 junior to 0.750 
con in 180 days)

1-3 trainees with 1 consultant (surgeon): 0.002 per day general; ~0.008 per day surgeon 
(125 days to get specialism) (general goes to 0.004 after specialism obtained)

Trainee's attention to detail, consultant's skill, and a triangular distributed random 
number affect skill gained +-10% (individual to each trainee)

Trainees in room over 3 lower skill gained by 2/n-1 per trainee

Skills taught lower skill gained by 1/skills taught (generalist skill counts as a 
skill)

Minimum award is always 0.001

The max skill a doctor can have to get surgeon certification is ~0.5 at the start 
(teaching all 3 specialisms at once to <=3 trainees).

(Another comparison is Cons. Psychiatrist with trainee psych skill per day: Before PR - 0.0118; After PR: - 0.0105)

Please do test this as I need to know whether the balance is correct. If you need a good level in the main game try Level 9

[lewri]

As Alberth said, we're not likely to get balance testers until the PR is in the game so I've marked as ready.

If we're merging let me know first so I can remove all the comments for the wiki.

[lewri]

Wiki comments removed now ahead of time. You can view them still under 98bb983 as removed lines.