Arsenal Extension - Spreadfire Cannon

Adds a new weapon to the game inspired by Descent 1's Spreadfire Cannon. The Spreadfire cannon is an energy weapon that alternates between a blast of three tightly-grouped shots, then three loosely-grouped shots. Works decently well against large groups of enemies. Spreadfire cannons can be found anywhere that a plasma gun can be found. === Thanks to TESLA for the turret for the thumbnail! The in-game Spreadfire Cannon will look similar to a standard plasma gun.