This is fairly important, it changes the default mode for what status
events are logged to INFO. It had been set to WARNING and INFO was relatively
unused.
This also removes expected support for RocksDB 'in-memory' databases.
If a shell-user requests a database via CLI flags it will now work.
This includes a minor SDK refactor as it move quite a few specialized
functions and facilities from core.h into system.h. There was a breaking point
for needing to frequently update core includes.
The new logger systemLog function allows a call site to bypass logging config
and write a line to the OS logger (aka syslog).
The initialization of a logger plugin was confusing. The 'init' step was
introduced to allow a daemon to buffer status events before a logger plugin
is determined by external/remote configuration. The buffered statuses could
then be transferred via a medium other than Glog (the default). To determine
if Glog should continue to write statuses to the filesystem the 'init' method
returned a Status.
Logger plugins should now use a feature method override to select how status
logs should be handled.
Previously, `ConfigParserPlugin`s could only maintain an internal derived object called `data_`.
Then parts of the code that knew to use the plugin's data would call `getParsedData` and provide the name of the plugin.
Parser plugins can now request a mutable version of the `ConfigData` using `::mutableConfigData`.
This requires a lock on the `ConfigDataInstance` and must be provided to their mutable accessor.
Acess to a mutable config enables parsers to make modifications to internal config structures like options and the query schedule.
