Balanced Spawning

Since I have been making this game a little more difficult as I went along, I think I should probably have powerups; such as ammo; spawn more frequently than health and missiles, for instance.

This can be accomplished by creating a new Coroutine in the Spawnmanager script, such as:

We, of course, will need to add a couple of new variables:

In order to start this Coroutine; and, be able to stop it; we need to add:

to the StartSpawning() method of the Spawnmanager script.