Multi-button actions

[UndeadTwo]

I've done some refactoring to make the code base a bit cleaner, and implemented chording (a name for multiple simultaneous button presses as a single action) for binary inputs. Currently, analog inputs (sticks and triggers) aren't tested and are not expected to be supported for chording. Please review these changes and let me know any additional changes you'd want made before you're ready to merge this into master.

[Lydzje]

Thank you so much for your contribution, as soon as I review the changes I'll let you know.