Add sifting appender to split logfile by thread

With this commit, the log for each thread in multi-threaded automated tests
should be stored in its own logfile simplifying the result parsing. The thread
is removed from the appender pattern to prevent duplication.
Add debug level info to the logfile

This should ideally simplify detection of errors
Log unsuccessful metadata result using the ERROR debug level
merge dev_5_0 -D org: PR 1112 (LogbackTools: silence ClassCastException traces)
merge dev_5_0 -D org: PR 1113 (CI logging improvements)
merge dev_5_0 -D org

Repository: openmicroscopy/bioformats
Already up-to-date.

Merged PRs:
  # PR 1112 joshmoore 'LogbackTools: silence ClassCastException traces'
  # PR 1113 sbesson 'CI logging improvements'

Generated by BIOFORMATS-5.0-merge-daily#830 (http://ci.openmicroscopy.org/job/BIOFORMATS-5.0-merge-daily/830/)