Add Journal unit test
[FOLD] Test Journal::Stream bool conversion
Remove per-Journal severity threshold to fix defect
[WIP] Add a new PartitionMap.
This will eventually replace the static linked list of LogPartition stored within LogPartition.
[WIP] Experimenting with plugging in PartitionMap
Not ready for prime time.
[WIP] Move logfile into the application.
Also beginning to isolate LogSink in anticipation of removing it.
[WIP] Move logging data from application to config object.
This is necessary because we need to log from a ripppled
which is parsing rpc commands, and this instance does not
have an application object.

WriteLog has been preliminarily hooked into the new Log
object (temporarily named NLog), and tests are showing that
logging is generally working as desired.

beast::Journal now needs to be pointed at NLog, and Journal
should not maintain its own partition map data (e.g.
partition severity thresholds).
[WIP] Move ShouldLog and CondLog over.
Initial Take 2
[WIP] This has beast::Journal partially responding
to dynamically changing severities.  I'm not 100%
positive but I suspect that the operator bool on
Journal is not responding.  Experiments with the
OfferCreate partition do not appear to output debug
logs when the debug log is guarded with
if (m_journal.debug).