`code/setup.dm`:
Fixed large amounts of indenting.
Fixed large numbers of comments and their clarity.
Added parentheses to macros using expressions.
Added FIXME for unused duplicated macros, without certainty of their requirement.
Removed some duplicate macros present. (`BRUTE`, `BURN`, etc.)
Removed macro `PI`, and replaced instances of its use with `var/const/Pi` from `maths.dm`
`code/global.dm`:
Fixed large amounts of indenting, added newlines to long single-lined list definitions.
Slightly clarified comments.
Takes a pass at updating ATMOSPHERICS to take advantage of the new powernet changes.
Also removes var/on definitions from many atmos machines. Machines generally shouldn't
be doing "on" things if they aren't using power, and most players don't expect a machine
to use power if it isn't "on," so I guess this is fair game.
Also, further refactoring.
In particular, gas_mixture/remove() was not accounting for
group_multiplier when determining the maximum amount of gas to remove
Also cleans up the interface for gas_mixture/heat_capacity().
