Pop the Corn: Kernel Clicker

Fixed an issue where the players currency would loop to -$2.147 Billion after reaching $2.147 Billion, this was due to the data type being int, which has an integer limit and will loop back around causing the issue. Changed it to long which supports almost infinite amounts of numbers. Increased the price for the butter and salt upgrade as they are very strong and broke the early gameplay. Increased rainbow popcorn drop chance, and it's multiplied value. Fixed an issue with Salt and Butter Multipliers affecting all purchases and rewards. Added Descriptions to Salt and Butter Upgrades for clarity.