Backfill logging

Log not only the count of jobs tested since the last time locks
were released, but also the total job count since the backfill
scheduler started.
Add DebugFlag of BackfillMap

Add DebugFlag of BackfillMap. Previously a DebugFlag value of Backfill
logged information about what it was doing plus a map of expected resouce
use in the future. Now that very verbose resource use map is only logged
with a DebugFlag value of BackfillMap