[OE-core] Patchwork cleanup

[Burton, Ross]

Hi,

I've started running the patchwork post-receive hook manually and
marking as submitted many patches in the queue, but as there's 132
patches of patches still (down from 140-odd!) in an attempt to restore
sanity to the oe-core I think we should just mark as obsolete every
patch that was submitted before a cutoff date, say 1st January 2014.
Any thoughts?  As much as I'd love to ensure we didn't drop an
excellent patch from 2012, I'm not going to manually check all the
patches that the tool can't find automatically...

Ross