Exempt meta from gblocks

Meta is the central co-ordination wiki, all global blocks come out of meta and can only be removed from meta, same with global IPBE requests. Therefore, we should perhaps exempt meta from global blocks so people can actually request global IPBE in an open environment rather than contacting stewards and allow IPs themselves to contest such blocks.

If a global block needs to apply to meta, then it can be locally blocked with appropriate options enabled. Plus global blocks are not that flexible therefore for users and IPs, contesting blocks are not possible (well IPs not at all).