Move old CASTOR documentation out of CTA repo

In the CTA repo, there is a directory ./tapeserver/castor/tape/doc/ which contains various bits of CASTOR tapeserver documentation, CHEP papers from 2012, someone's diploma thesis from 2005, etc. As this was buried deep in the source tree it was missed when we separated out the CTA docs from the source code.

We should move this documentation into the docs repo and remove it from the CTA repo.