[Finished!] 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)
This PR should be pretty much done. At this point I'm confident that I've reviewed all occurrences of blood in the game to make sure they spawn the correct type of blood. Given the limitation of colors, I likely won't be adding more types of blood or gibs, however I might change their naming if I get feedback on it.

NOTES:
* Recategorizes insects as being 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 mammal meat when butchered. For now, though, insect butchering returns are untouched.

KNOWN ISSUES:
* Some monsters, particularly big ones such as bears and moose, will rarely generate no blood when their corpses are (s)mashed. This issue has been present since smashing corpses was made into a player activity, and unfortunately I was not able to fix it.

POSSIBLE ISSUES:
* Needs testing with a tileset on, as I have never used one.
* Changes insect monsters to a new material. I've carefully included it in all checks that targeted specific materials, so I think this shouldn't be an issue.