Release notes

Improvement: implicit SparkSessionWrapper renamed to AtumSparkSessionWrapper in order to prevent name clashing.
Generalization: S3Location Utils moved to AbsaOSS/commons, so a migration for S3Location-related routines is needed:
- needs dependency za.co.absa.commons:commons_2.11:0.0.27 (for Scala 2.12 use commons_2.12)
- za.co.absa.atum.location.S3Location -> za.co.absa.commons.s3.S3Location
- za.co.absa.atum.location.S3Location.StringS3LocationExt -> za.co.absa.commons.s3.SimpleS3Location.SimpleS3LocationExt
- address small API differences:
  - "string".toS3Location -> "string".toSimpleS3Location
  - s3Location.s3String -> s3Location.asSimpleS3LocationString
Added support for Apache Spark 3.1.X
Atum model now has json4s dependencies as provided dependencies to accommodate multiple Spark versions. More details in the README.

Issues fixed