added array_each() helper
removed unused circle_collision.js
added pointInCircleSector() function

that was a pain in the ass...
added pointInCircleSector() debug lines
beginning to add melee weapons
added knife gfx/sfx
beginning to make knife (melee weapon)
added helpers for various math-related stuff

- converting degrees to radians and vice-versa
- function to normalize angle onto (0, 2 * Pi)
- function to check whether a number is in an interval (non-inclusive)