206 - Hero instances

Hook up hero instances based on enemy instances. Create an update function which just initializes one hero. And a draw function. Bullets should be handled automatically if the source data is mapped correctly. Fix an issue with the hero_instances schema. (Not actually assigning a capacity.) Change a constraint. The hero bullet update rate is very high, which spawns a lot more than the expected constraint of 255 maximum per wave. Adjust the allowed count to 16 bits. But all the same, the rate is probably too high anyway, so reduce that to be balanced again later. Use the mouse position to set the position of the first hero instance.