support NSDI06 easily, we want to create a project called NSDI06, have
anyone who has an NSDI deadline join that project, and use that
membership to allow them to swapin experiments in their real projects.
So, new global_policies entry format:

	insert into global_policies
	     values ('membership', 'emulab-ops,testbed,NSDI06', 'eq', 0);

When this policy is inserted, only members of the comma separated list
of projects names can swap in *any* experiments.

Just remove the table entry to remove the retriction.