Update d2/d2srv developer doc
Some code was moved from src/bin/d2 to src/lib/d2srv. This is now finished but the dev doc (src/bin/d2/d2.dox) needs to be update to reflect file moves.
- update d2.dox
- update gss_tsig.dox
To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information