add 2.12.x jobs

[adriaanm]

• on our end, just add 2.12.x to the array

  scala-jenkins-infra/recipes/_master-config-jobs.rb

  Line 58 in fc2872f

  %w{ 2.11.x }.each do | version |

  loops over
• merge jobs/ from 2.11.x to 2.12.x
• make default values of job params depend on the target branch (e.g., jvm flavor & version), see Fix #4: multiple JDKs #19

[adriaanm]

The only 2.11.x thing about the jenkins jobs is their name, since the logic is determined by the scripts, which are in the repo, and the gitref/jvm/... is specified by parameters passed to the job.

Once we test merge commits, we should add a parameter for the merge base.

The main reason to have separate jobs is to make it easier to look at the logs in jenkins. If we could have views that group builds by parameter values, we wouldn't need multiple jobs.

[adriaanm]

Closed by #53 and #63, #64.