[PREVIEW] Sonar Groovy 1.7-rc1

Hi,

I finally found some time to work a bit on the Groovy plugin. Nothing groundbreaking, some minor fixes here and there, removed some deprected classes & features. Should be compatible with SonarQube 7.8-8.9 (at least unit tests pass with different versions :wink: )

Pre-release notes are here: Release First preview for 1.7 路 Inform-Software/sonar-groovy 路 GitHub
Direct download: https://github.com/Inform-Software/sonar-groovy/releases/download/1.7-rc1/sonar-groovy-plugin-1.7-rc1.jar
SonarCloud report: https://sonarcloud.io/dashboard?id=org.sonarsource.groovy%3Agroovy