* Hardcoded autofire plugin
* Changed register_frame to register_frame_done, removed pause check
* Added support for multiple buttons loaded from a file
* Implemented saving settings on quit
* Fixed multiple keybindings for same button from overwriting each other
* Replaced double-quotes with single-quotes
* Refactored saving/loading into a separate module
* Changed button format to use input_code rather than string token
Settings format is unchanged (still saved as string token).
* Rewrote table initialization in save/load
* Implemented menus
* Added helper messages for "on frames"/"off frames"
