More Elites + Boss Rush Mode

Adds 2 new elites as well as a new game mode with 1 new boss. To play it select the new Boss Rush mode after selecting the difficulty Concepts are by Psina and me All art is by Psina, big thanks to Psina !! NOT compatible currently with SomeSeriousWork mod, Pentato and Witchery !! _____________________________ current version : 0. 2. 8 new stuff: - Boss Rush button now comes after danger selection - Fixed a bug where Boss Rush wins would override a character's Danger progression. Boss Rush progression is now separate - Ink Sniper jumps less often, moves slower during phase 2 and faster during phase 3. Ink shots effect modified. - Halved the spawning of tree and loot aliens - Fixed minor bugs happening after the special boss is dead - Fixed the bug where UFO Boss was broken on later endless waves - Added a small hitbox on the UFO Boss when it falls to allow bull to get hit