Xroot permission validation

[btovar]

For #685

Please make sure that the following items are taken care of if needed:

• Has the database format changed? (renamed or new columns, tables)
  Or did any of the project layout change? (files required to run the
  workflows)
  • Please increase the version number VERSION after the imports in
    lobster.util. This will ensure that Lobster does not try to load old
    projects with an incompatible version.
• Did the required Work Queue version change?
  • Please update the three version numbers in doc/install.rst. Adjust
    the tarball name in the install_dependecies.sh script, too.
• Are all additional dependencies in setup.py?
• Mark any issues as closed either in commits or in this pull
  request.