Applicative

Hey Joe, here is a little better implementation of <*>, but there is another problem which I'll probably let you deal with, unless you'll want me to work on it.
In function 'pure' image created of size 1x1, which makes it impossible to apply with other size images. Applicative stuff won't work without it, for instance function 'sum' that sums all elements of the list will give an error on summing list of images. Basically some kind of Unit Type image is necessary that if any operation done on it will return the other image it was applied with, like: 
image + UnitImage = image