Logging

Very basic server-side logging implementation. This defines three loggers, nodenet, world, and system, and rotates 1000 log messages for each of the loggers in server memory. Clients can fetch the log messages from /get_logs using logger and/or timestamp filters.
Native modules have access to the nodenet logging facility through netapi.logger

We can either add client UI to fully fix RUN-7 before merging this, or merge it now and work directly with /get_logs in the browser for now, which is better than nothing.