Framework for defining menus modularly

Custom framework, similar to a levelscript or behavior script, that allows for easier creation of custom menus for hackers.
Should support:
- Callbacks
- Submenus
- Input types (numbers, toggles, etc)
- Different text engines

Mockup code by @thecozies (would be passed to a function such as `render_menu(x, y, pauseOptions)`):
```c
struct SubOptions modelOptions[] = {
{ .label = "big chungus", .value MODEL_BC },
{ .label = "luigi", .value MODEL_LUIGI }
}

struct MenuOptions pauseOptions[] = {
{ .callback: set_mario_model, .options: &modelOptions },
...more options
};
```
Possibly take [this menu code](https://github.com/aglab2/hacktice/blob/master/src/cfg.c) by @aglab2 as reference.