Seperate out unnessecary functions from library

[luigi311]

Looks like you are doing a lot of things in your library which shouldn't really be done in the library section. For example you have functions that will collect all images in a folder and return the path, this has nothing to really do with the stacking functions. The stacking functions should just take in an array of images already good to go and the stacking functions just need to do the processing. Those preprocessing/helper functions are probably more suited for being in the example code only so users can see how to use the function.