Implements gibs and blood for insect and plant monsters.

Behold! The latest technology in chunkyness: Now you can enjoy pulping up triffids and giant ants just as much as you enjoy pulping up zombies. 
Plant gibs and their names were already implemented, but I had to take some liberties with the names and colors of the rest of the content (feel free to improve/discuss, took some feedback from the IRC first)

NOTES:
 + Recategorizes insects as made of "iflesh" rather than "flesh": This makes it trivial to add insect meat in the future, to stop bugs from dropping good ol' chunks of meat when butchered. For now, though, insect butchering returns are untouched.
+ "Hemolymph" means "bug blood". Yes, it's grey.

KNOWN ISSUES:
+ Some monsters, particularly big ones such as bears and moose, will not generate any blood when their corpses are (s)mashed. This issue has been present since smashing corpses was made into a player activity, unfortunately I couldn't fix it.

POSSIBLE ISSUES:
+ Haven't tested these changes with a tileset on. I made some changes for them to work, but again, I haven't tested them: needs confirmation.
+ Changed insect corpses to a new material, I'm not sure if this could break anything. Butchering them still works as intended.