Add timestamp to each log message

This originally seemed desirable to simplify logs, but having more precise info would be useful.

Prepend each message with the millisecond timestamp, in addition to the human friendly timestamps that are printed: https://github.com/usgs/pdl/blob/master/src/main/java/gov/usgs/util/logging/SimpleLogFormatter.java#L73

Not sure whether this is considered a breaking change, since it would affect log parsing, and should be configurable.