A few fixes/protections in the PROOF tutorial steering macros:
     - Make sure that the dir paths for selectors and PARs are always correct
     - Add possibility to force '++' mode as a workaround to the usual problem of fake dependencies
     - Add a check on the running mode and refuse to run if not compiled (the checks for running daemons
       require compilation)


git-svn-id: http://root.cern.ch/svn/root/trunk@31832 27541ba8-7e3a-0410-8455-c3a389f83636