Fix issues with releasing cross versions of Scala and Spark using maven

[morazow]

Situation

We would like to release different versions of the connector for recent Spark versions. For example, Spark 3.2 with Scala 2.13, Spark 3.2 with Scala 2.12 and Spark 3.1 with Scala 2.12 versions.

However, it is not very easy using maven. There are several issue:

• Correctly setting artifactId and version, for instance, com.exasol:spark-connector_2.13:1.2.0-spark-3.2.0
• Rewriting pom.xml for Maven Central, that sets correct Scala binary version for dependencies

For references: https://www.hammerlab.org/2017/04/06/scala-build-tools/#a-trying-and-failing-to-scala-cross-publish-with-maven