[JENKINS-23365] Draft SCM-Job rework.
Can now override guessBrowser.
Reduce log level.
Updated to core API changes; require updated multiple-scms-plugin to work correctly.
Updated to released dependencies.
Nothing “to do” about a dependency on matrix-project.
Merge pull request #59 from jenkinsci/SCM-Job

[JENKINS-23365] Work in a general Job