unit_cost and nosub_unit_cost
remove nosub_unit_cost
_allow_sub optional param
Unify check macros to CHECK_EDIT_ALIGNMENT_ARG
add -O for normal build on examples
rework envelope pruning as an optional heuristic
beam -> edit_beam  &&  prune_bias -> cost_beam
run_min shall be magic constant for now
default cost_beam_checker update() is const
excise default_cost typedef, just use unit_cost
excise edit_types.hpp