Create release strategy for EMX-downloader

[sidohaakma]

At tihs moment we build a version by changing the version in the pom.xml build the jar and upload it to github.com.

• Not reproducable
• Prone to error
• Possible not running automated tests

Possible solution

• Publish it to sonatype in MAVEN flow (no manual work anymore)
• Create Jenkinsfile with release flow (see molgenis-ops-tools repo)
• Create release notes on github.com