JENKINS-24735 - Add support for build parameters in Subversion URLs

 * When creating a feature branch from a project that supports
integration from new feature branches, take into account system and
project environment variables
JENKINS-24735 - Add support for build parameters in Subversion URLs
 
 * Extract SVNUrl variable expansion into a utility and use that acrosss
all classes that require it.
Merge pull request #2 from alexouzounis/JENKINS-24735

Jenkins 24735