Optimized Sniper Scope

While the old sniper scope looked nice it had a bunch of problems:

• It needed two cameras and everything had to be rendered twice, causing big frame drops when using the scope
• Enemy markers didn't work when looking through scope
• The image in the scope wasn't very sharp

The new scope is a lot simpler. It uses just one camera and an overlay texture for he scope and crosshair. This means it now has the same performance as any other gun.

I've made a new build (0.0.9) with the optimized scope which also contains the following changes:

• Stop aiming mounted MGs when reloading
• It's now possible to go to top MG from commander position in Panzer IV by using mouse wheel
• Added dirt mask to vehicle scopes
• Stop aiming while going to prone
• Fixed bug where client couldn't equip gun after shooting Panzerfaust
• Bots can now shoot crew members peeking out of armored vehicles