make torch light additive, versus only the most recent torch

having a bright radius and the older ones being faded more.
don't add to the fragcolor, assign. otherwise it's kind of undefined.

i presume my nvidia drivers don't whine thoughh because they're too
lenient
quiet debug a bit
add shitty wooden pickaxe (programmer art ftw)
improvements to torch sprite and add awesome steel pickaxe

courtesy of prohobo in #reddit-gamedev