Add swap moves into the mix.

Need to re-benchmark.
Don't recalculate the information we already have.
Extend the start date to the upper bound on the horizon, not the actual
horizon.
Tiny perf improvement in score calculator plus easier profiling.
Minor update to the scoring function to make it more fair.
Gather predecessor info in advance.

Significant performance improvement.
Rebenchmark
Upgrade to latest Planner 6.0-SNAPSHOT
Give the solver more leeway in assigning jobs to overrung project
horizon.

This brings us MUCH closer to feasible on A-10 (6 hard broken) and A-7
(still hundreds broken).