User friendliness all around

More changes to make the game more user friendly! Very (VERY) few sales, but nice and plentiful feedback overall!

• Added Vsync option. This will lock the framerate to your screen's refresh rate, which should make the streaming experience smoother. Some particle effects look a tad worse at a capped framerate though, I'll investigate why at a later time.
  
• Turned the values from the config menu into something more human readable. Most importantly the deadzones have more understandable numbers, they used to range from 0 to 32000, which most players found confusing. They now go from 0 to 64, so changes are more noticeable.
  
• Simplified the first few shielder levels further. I saw more people getting stuck there, so I made it clearer where/how to throw the husk to solve the puzzle. I couldn't find a way to simplify them further without killing the challenge, so I released a walkthrough of the levels in case people are still unable to go further.
  
• Updated SDL2 version.
  
• Fixed minor bugs.