[Gzz] One more new file format ;)

[Tuomas Lukka]

Since we need to amend the file format anyway (due
to the vstream change and preflets), we thought with
Benja that we might just as well move to yaml (www.yaml.org)
at the same time. 

The cell id formats need some thought, I'll just write cid1 and cid2
for them below.

structure:
        dimid1:
                disconnect:
                        - [ cid1, cid2 ]
                        - [ cid3, cid4 ]
                connect:
                        - [ cid2, cid3 ]
                        - [ cid4, cid1 ]
content:
        cid1:
                - spanid
                - spanid

etc.

        Tuomas