Added debugging scripts that work with detailed cache.log

Added debugging scripts that work with detailed cache.log

  scripts/find-alive.pl: pinpoint objects that are still alive, to find leaks
  scripts/trace-job.pl: find cache.log lines that correspond to a given job
  scripts/trace-master.pl: trace jobs related to a single master transaction

The scripts require maintenance as the logging format changes, but
they often simplify debugging by extracting relevant information from
tons of poorly structured cache.log data.