Add mode presets (accuracy and compatibility) to simplify enhancements settings

[bsnesFan]

lsat.1.mp4

V2. I did some changes because of this comment: #158 (comment)

When a game is loaded, you will get an information that you should reload the game in order for all changes to take effect. If no game is loaded, you will not see this, because the changes will take effect immediately. It's working really good and I think with that user will better unterstand what they have to enable for a good gaming experience.

Other than that, I'm not sure whats the best way to describe these two mode presets, but I don't think something like:
Performance mode: Maximum speed, [...]
is right, because it isn't just about speed, that's why something like "Prefer HLE" is disabled. We should come up with something appropriate, so people want to use this mode by default. You can decide what's the best way to do this.

Thanks again for your help, Screwtape. :)

Fixes: #113