Some major refactoring has been going on.
Added simple structs of data containing info about what action to take when a menu item is selected.
Finally removed all but one call to display.display() in menu-function. There might still be more than one call to it on a frame though, since some functions still calls it internally.
* Broke up the code into more general functions instead of duplicating code
* Made stuff const and removed variables no longer used
* Use defines for menu button values
* Changed the order or things to avoid forward declarations
* Use array lookup instead of switch-case on some menu options
* Adjust menu functionification
* Cleaned up sensor rendering