ScratchCPP Render 0.3.0

Change log:

• Refactored rendering to cache costume textures (#63).
• Implemented the bounding rectangle method - "if on edge, bounce" now works correctly (#60).
• Implemented all pen blocks except the stamp block (#25, #28, #29, #33, #34, #30, #31, #32, #35, #75, #74, #73).
• Implemented the color, brightness and ghost effects (#15, #20, #21).

Full Changelog: v0.2.0...v0.3.0