New Character Abilities and small balance change

Each Character now has their own special ability along side the slow time ability that all characters have. Nova - Sprint Boost - Sprint faster for a short time Natalia - Detonate - Creates a large explosion that damages enemies in range David - Barrier - Generates a barrier that blocks all damage John - Smoke Cloud - Makes a smoke cloud that slows all enemies Balance changes - As I was playing myself i started to get frustrated that i could never afford the damage upgrade so i replaced the speed upgrade and the damage upgrade prices. Damage upgrade now costs 5k per upgrade. Speed upgrade costs 10K for the one upgrade