Improve Logging configuration in the Starter

[jxblum]

This task will encompass:

• Break up the SLF4J / Logback configuration by Appenders, Loggers, Properties (Variables) and so on.
• Introduce well-defined Properties (Variables) for things such as the Appender pattern in addition to log levels.
• Integrate (include) existing Spring Boot SLF4J / Logback configuration files
• etc