introduce error for dark edges

dark slice edges are usually image edges.  introduce error so they don't
get accidentally matched.
add makefile to project
accept solutions smaller than the original

when testing small thresholds, accept the incomplete result
begin attempt 2, find starting tile
add second tile
remove impossible matches from map
find next best match attached to a placed tile
place third tile
do cleanup after placing that tile
haha, fix logic of step 1 and 2
refactor step 1 to resemble step 2
combine step 1 and 2
extend and fix placing wrong tile
cleanup, move more variables up to configuration section
Merge branch 'attempt-2'