Refactored firearms, bullets; bullets are launched using AddForce()
Removed Vector3Extensions

- It appears as though passing a Vector3 to a function or property that calls for a Vector2 (or vice versa) works without issue.
Prefer the use of Vector2 wherever possible.

- When performing mathematical operations on vectors, it is possible to cast a Vector3 as a Vector2.
- ex: (Vector2)transform.position + rigidbody2D.velocity