Medium-size update - batteries and upgrades

This update fixes some common criticism about upgrades, should greatly help with onboarding new players about the battery mechanics, and also adds a few augments with a fun, active playstyle in the process. The game now has almost 80 total augments, which is nice. [b]upgrades:[/b] [list] [*] upgrades now show text vaguely describing what the upgrade does [/list] [b]pickups:[/b] [list] [*] upgrade pickups that drop from beating elites no longer expire [*] other pickups fade slightly over their lifetime to indicate they will go away [/list] [b]batteries:[/b] [list] [*] BDC warning about bad things that happen when you run of of juice are now more visible [*] lack of juice kills you more slowly [/list] [b]new augments:[/b] [list] [*] overcharge [*] explosive charge [*] extra oomph [*] artemis accumulator [*] celebration [*] brood batteries [*] one with the brood [/list] [b]balance[/b] [list] [*] lategame bossess have somewhat more HP [/list] + minor improvements to sound and graphics