Remove redundant teiCorpus and corpus-level teiHeader elements

[ninpnin]

Fixes #227

• [x] Run on small subset and push
• [x] Check that the subset is correct
• [x] Run on the rest of the data

The diff is going to be very large.

[ninpnin]

• [x] I have checked 50 protocols sampled by Bob.

[MansMeg]

Cool, so merge then?