Added Rex Boss at levels 25 and higher

Added jeremy the badass nuke riding shark as a spawnable enemy during the rex boss fight

Rex has 500 health and spawns a nuke riding shark every 5 seconds; sharks cannot be killed and will remove 500 coins upon their explosion

Changed boss spawn behavior to be bounded between 2 coin values so if you use dev mode to skip ahead you don't have to fight all the previous bosses

Added spawner menu dev tool

Added invincibility dev tool