Add problem 36 description (Projectiles Life Span)
Make projectiles moving

Now firing projectiles moving with kProjectileSpeed speed in direction
which player are facing.
Add projectile lifespan: 3.5 tiles

If projectile lives longer than 3.5 tiles than PolarStar method which
updating projectiles resets this projectile.
Add two projectiles living currently

Not more than two projectiles of PolarStar can live in the same moment.