Centrist (V1.09)

Just added some alternative controls. Although i found mouse controls akward to use, so i might remove them later :D 
Tuned down difficulty ramp up at later levels. Early levels are still fairly similar.

• Difficulty will ramp up slower at later levels (increased number of blocks required for maximum difficulty from 350 to 520)
• Added alternative "WASD" for alternative controls
• Added mouse for alternative controls (Move cursor to move blocks side ways)
• Left mouse button for faster falling
• Right mouse button for block rotation