Add Percentage Gap and Option for Splitting Logic

[Neuffexx]

Will need to add an option to the Menu bar to interpret the input of the Gap input to be used as a percentage rather than a pixel count.

• Will be default option (because its more intuitive for most people)
• Needs to be clamped from 1 - 100%
• Will need to be done within the ProcessImage function
• Will need to create a new Settings option in the Menu Bar

[Neuffexx]

As I am currently working on the Settings menu for the Menu Bar, create a temporary variable to store the selection of the input mode.
Then simply add a menu bar button to the File menu. With which you toggle the variable.
You can find how to do so in the create_menu_bar function.