[NOTICKET] Overall project enhancements

• Everything on ch/cern/monitoring was moved to ch/cern/monitoring/utilities to match the package declarations.
• The method writeStream on KafkaUtils was changed to:
  • Return a StreamingQuery instead of a Unit
  • Configure the outputMode which can be passed as a parameter (defaults to Append as before)
• A few changes recommend by IntelliJ were carried out to:
  • Remove redundancies/unused imports
  • Adhere to Scala's coding style