Restored wall smash feature
Preparing for wall_smash of multiple images
wall_smash improvements

`wall_smash` must make use of an array of "target" indices for the left side of the shifted subject. It must also be aware of the length of the subject's image so that it doesn't bother shifting over more pixels than it needs to.
fixed reaveal_edges stepping on other mutations
Added background sample options to ckiss script

* users can provide a value (or r,g,b values) instead of having the program sample background values automatically
* users can provide a side of the image for the program to sample from (in case one side intersects with the subject, for example)
Edge optionally uses a predefined background val
reveal_edges should process edges before mutating
Merge branch 'better-smash'
Added test for invalid edge config keys
Removed dead code

A sliding window won't be needed after all.