[JENKINS-15918] RunParameter environment variabes contain . character
[JENKINS-15918] Adding some detail of the Environment variables created
[JENKINS-15918] Updating unit tests
[FIXED JENKINS-15918] follow-up changes

- Environment variables are by convention upper case, so I'm switching to upper case. This was what the original ticket requested anyway.
- Since the ".jobName" was never documented to begin with, let's not promote that and stick to "_JOBNAME" as the official version.