Properly quote executor file paths cause $WINDOWS
Properly escape backslashes in generated Groovy code

This will prevent Groovy errors like:

  org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
  Script1.groovy: 1: unexpected char: '\' @ line 1, column 4.
     "C:\jenkins"
Allow `jenkins_slave` to be used as a standalone resource

This is useful in situations where you want create a slave instance on
the Jenkin’s master but still control creation of the underlying service
resources.