Added Patriot missile for possible future use 

Patriot missile is for the possible future inclusion of the Mobile SAM vehicle. 
I have been playtesting with others using the Mobile SAM vehicle, and everyone so far has liked it. It provides air defense and provides a counter to heli spam, but doesn't negate helicopters' usefulness.

The purpose of the proposed MSAM is to reduce Nod's need to rely on bike spam or E3s for air defence. (Stealth Tanks can work, but it's a late-game unit, and not accessible the majority of the time).