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.

upgrades:

• upgrades now show text vaguely describing what the upgrade does

pickups:

• upgrade pickups that drop from beating elites no longer expire

• other pickups fade slightly over their lifetime to indicate they will go away

batteries:

• BDC warning about bad things that happen when you run of of juice are now more visible

• lack of juice kills you more slowly

new augments:

• overcharge

• explosive charge

• extra oomph

• artemis accumulator

• celebration

• brood batteries

• one with the brood

balance

• lategame bossess have somewhat more HP

+ minor improvements to sound and graphics