disable edit_alignment() related code to prep for rewrite
rewrite of dijkstra_sssp_cost() to take advantage of clever trick from: 'An O(ND) Difference Algorithm and Its Variations'
tweak variable convention to be saner between cost and alignment functions
draft of edit_alignment() compiles, stubbed out unit test
edit_alignment() passing most unit tests.  prio-queu causes new ordering of operators, which may not be repeatable without expensive stable-queu option, I need order independent checks for correctness of edit scripts