Endless Mode Improvements!

[list] [*] New wave logic: enemies killed instead of by time [*] Enemies will be wiped between waves [*] Added more time between waves [*] Challenge waves now drop special loot boxes :) [*] New weather event: Fog! [*] Night and Day level modifiers are set from the start and are consistent [*] Critical hits drop ammo 50% of the time, down from 100% [*] Changed cost of Auto Turrets to 30 from 25 [*] Fixed bug where level 2 barricades would upgrade randomly [/list] New Fog Weather: [img]{STEAM_CLAN_IMAGE}/40809991/b25f30c44f7c0ccda26c1b057ade3190df753cd1.png[/img]