Enable branch analysis in Sonar

As a developer working on a branch, I want to be able to have Sonar check my work without that check effecting the Sonar report on the main project (master branch) so that I know my code quality is high, and when it's not it doesn't mislead developers looking at the main project into thinking the overall project quality has dropped.

• The sonar.branch property is deprecated in 6.7: https://docs.sonarqube.org/display/SONAR/Analysis+Parameters documentation seems to suggest to use the (paid) Developer Edition.
• There is the Sonar Branch plugin available in the Developer Edition, however this is a fee product: https://www.sonarsource.com/plans-and-pricing/developer/

AC:

• Figure out how to do this in Sonar (it seems to have changed in 6.7, and might require upgrading to 7+)
  • using the deprecated feature might be the only path forward if we can't buy the Developer edition.
• Make it work