Glowshroom Reworking

Fixes the bug with effects/glowshroom not glowing when placed.
They don't spread infinitely: The odds of a shroom spreading decreases with each generation. Because they're sane now and not virally-spreading fungal horrors, they've been changed to spread on normal station floors and not just the asteroid.
The spreading glowshrooms acquire the parent's stats, with some mutations.
The delay variable is now based off of production, and goes DOWN with better stats instead of GOING UP.

-Removes unnecessary (copy-pasted) code bits in walking mushroom/killer tomato code in grown.dm