solving issues related to JENKINS-10628 / JENKINS-16116:

solving issues related to JENKINS-10628 / JENKINS-16116:
 - doCommitNotification considers GlobalNodeProperties environment 
variables before checks of svnUrl
 - repositoryLocationsNoLongerExist check
within scmPolling considers GlobalNodeProperties environment variables
before checks of svnUrl
 - doCommitNotification does not cut the first 4
characters of SVNUrl in order to Cut the "U " from the "U
/your/changed/files" string instead it cuts the first character and
trims the string. this was needed for compatibility to either
post-commit hook or svn-version (didnt analyze this that precisely)