Weight threshold fixes:

1. The bodyguard will now use a weight threshold of 130 when evaluating slaves for combat suitability, in line with the actual mechanical deadliness threshold.
2. Removed the extra weight 100 guard from long term effects.  Note that slaves with weight between 95 and 100 are now eligible for the smallest health penalty (previously restricted to weight between 100 and 130).
3. Adjusted the weight SMR to do what it says on the tin.  "Obese" (from the actual SMR text) means 130 or greater, so allow slaves between weights 100 and 130 even when this SMR is enacted.