[schema,server] add a security debugging aid (closes #2920304) - Add a DGB_SEC debugging flag (to be used with set_debug/debugged). - Add a context manager (tunesecurity) to filter security assertions. Note: this does not address all read-security mecanisms.

if not rql('CWConstraintType X WHERE X name "RQLUniqueConstraint"',
           ask_confirm=False):
    rql('INSERT CWConstraintType X: X name "RQLUniqueConstraint"',
        ask_confirm=False)