Review logging and log files

[ggalmazor]

Aggregate has some issues with how it logs messages:

• It uses stdout as log output channel, which then Tomcat pipes to its catalina.out log files. This produces a mix of Tomcat messages and messages from any other app users might be running in the same server
• Messages coming from different logging systems follow different patterns, which is confusing
• Some messages lack basic information about the date, time, and source of the message
• Some parts of the message are localized. some others aren't

Changes we would need to consider:

• Normalize message schema so that all messages include date, time, and source
• Remove any localized content and normalize to English all common message parts
• Produce a separate log file located at the Tomcat logs directory
• Configure log rotation

These changes will probably require adding SLF4J dependencies to bridge all the different logging systems our code and its dependencies use.