Outdoor Ambient Daytime Radiation Rework  

Reworks the "Radioactive air during daytime" option to stay relevant longer than the first 15 minutes of every new game.

The "Radioactive air during daytime" option in Gameplay.diff is neat, but stops mattering completely once you get anything other than the starter jacket and respirator. I thought this was kind of lame and decided to adjust the mechanic to stay relevant the whole game.

Reworks the daytime radiation gain formula to make it less oppressive in the early game, but stays relevant all the way to late-game.

- the outdoors is filled with a small, but constant amount of ambient radiation.

- while completely unprotected, you'll take a couple of rads per second when standing outdoors. this can be reduced with radiation protection (armor, meds, drugs, etc), but the effect never completely goes away.

- the ambient radiation is stronger during the day (1.0x), and weaker at night (0.5x).

- the ambient radiation varies in strength with the current weather conditions, following the table below:

["clear"] = 0.95x
["partly"] = 0.85x
["cloudy"] = 0.75x
["rain"] = 0.65x
["storm"] = 0.55x
["foggy"] = 0.3x

- if you are protected well enough, you'll be able to slowly outpace the incoming rads, but the rate at which you shed rads will still be slower than if you were simply standing indoors. (you'll need slightly more protection than an unmodified Ecologist SSP-99M suit to do this during the day, so use mutant skins and stuff for extra protection)

Compatible with all mods except anything that messes with level_environment.script, in which case you'll need to merge the code changes yourself. All of the changes are made inside function "update_radiation_day"