New RPG sprites

Stolen from Goon because it should be very obvious that you're holding a rocket launcher.

Old
![b](https://cloud.githubusercontent.com/assets/4674335/4302969/62556c48-3e60-11e4-82bf-dbc2d3ae98f0.png)
New
![a](https://cloud.githubusercontent.com/assets/4674335/4302970/6257e432-3e60-11e4-9581-d1cd72bfdb07.png)
Recolored to match projectile and ammo
![c](https://cloud.githubusercontent.com/assets/4674335/4302989/91ea2c5a-3e60-11e4-97ea-f03b34f41bbd.png)

And I gave the Xcom laser rifle unique 100/75/50/25/0 ammo sprites