Adjusted 'stitch' to accept a list of pores to stitch rather than two labels.  Also added the existing labels in the doner network to the recipient's labels by default, and 'stitched' to the new throats generated by the method.
Adjusted 'stitch' to accept a list of pores to stitch rather than two labels.  Also added the existing labels in the doner network to the recipient's labels by default, and 'stitched' to the new throats generated by the method.

stadelmanma/OpenPNM,amdouglas/OpenPNM,PMEAL/OpenPNM,amdouglas/OpenPNM,TomTranter/OpenPNM