Make table names for JdbcLog configurable

The current implementation of the JdbcLog (jdbc logger) hard-codes the resulting table names to be "messages_log" and "events_log".

The tables are hardcoded constants, and no calls exist to modify the name of the table.

I'd be ideal if we could specify the names of the logging tables in the config file (or programmatically).
That'd would allow for easy prototyping with Rails to log all the messages to the DB and easily display them in a webapp.

The constructor for JdbcLog takes in the SessionSettings object, so it can easily read the table names from it.