[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).