create helper function allowing to import an entire folder of spritesheets

[tsedan]

Basically create a function that takes in a directory with spritesheet images, and import them all, adding them to an animation component automatically such that each filename (with extension removed) becomes the name for that respective animationstate.
i.e.:
I have a folder with idle.png and run.png, each of which is a spritesheet in which the individual sprites are the same size.
I run "import_from_folder(folder_dir)" and it imports all of the spritesheets into an animation object with the names "idle" and "run".

[mrElnekave]

Done on this commit: e56ddc0