Mech Weapons researching.


Added the Mech Ion Rifle, Carbine and Rocket Launcher to the list of mech weapons you can build.
Added the normal Ion Rifle to the list of weapons you can build.

![guns](https://f.cloud.github.com/assets/6342371/1901724/9f057c1a-7c68-11e3-8d2a-41f5a9a27a7a.png)