Improve image splitting logic

[Neuffexx]

Analyze and think of ways to improve it, pretty arbitrary for now, but I am sure there are bound to be some things that can be improved.

[Neuffexx]

Either accommodate for 1 row or column(+ 1 row & 1 column) user input, or block it by setting the minimum input rows/columns to 2.

[Neuffexx]

need to check image for offset, and make sure that if any splitting/cropping coordinates go out of image bounds there is error handling so it correctly splits/crops without crashing.
See this Issue for more details.

[Neuffexx]

Image splitting primarily now works in a single function (calculate_image_split) that calculates and saves the image cells as well as the coordinates that were used to make them for the previewer to draw it as well.

• This function now just needs to be called by the relevant static or animated type functions as many times as needed and the save the results to disk.
• The Previewer simply said needs to retrieve the coordinates of the cells from the function output rather than the split cells
  • this also opens up the possibility for an alternate previewing mode, that shows the split cells directly, removing all the UI overlays and just showing the result or other previewing modes
    (will let me add an option for it into the menu bar, and then have a function that checks the selected previewing mode from the settings to choose a preview rendering function)
  • still need to update the 'update' function to actually utilize this new unified function

This provides a more uniform approach to splitting the images and calculating everything necessary.
Will make it much easier to maintain and alter in the future since no duplicate code exists that needs to be altered multiple times.

[Neuffexx]

Updated ToDo's for how to implement this approach now that a bunch of stuff was restructured/cleaned up.

However, the splitting and preview method would need to ALWAYS be the same then, which isn't a problem since it can still be adjusted in the settings menu, but requires the merging of the settings into a single unified input.