Medical side-effects now appear on overdose.

Also reduced anti-toxins pill amount, because 50 units is way too much for a single pill.
Chemical rebalance across the board.

- Halved metabolism in general. This is not a huge change, and will probably work out fine.
- Nerfed metabolism for individual chemicals, for example spaceacillin, greatly.
- Made mildly toxic chemicals, like pure carbon, cause medical side-effects.
Merge branch 'feature' of github.com:CIB/Baystation12 into feature

Conflicts:
	code/WorkInProgress/Cib/MedicalSideEffects.dm