rename ClientSession -> KDCSession

add ap_req generation to ApplicationSession.  This involved some
refactoring to get the core ap_req in a shared place.

add a simple barebones hacky zwrite client
comment fix
add initial (yet untested) nfold impl
Merge branch 'master' of github.com:mhorowitz/pykrb5
make the nfold tests pass

start implementing the dk profile, and 3des
add test vectors for hmac
remove unneeded local variable
finish des3 impl.  kvno works against des3 realm, and cross-realm also
tested.
rename krb5.engine module to krb5.tgs_client
delete dead code
update flufl.enum version
complete out ccache write impl
make kinit work.  tested for des and des3.

This includes necessary asn.1 support, string-to-key, preauth and
as-req/as-rep handling.

tgs_client could use some refactoring (and probably a rename)
only print renew until if set
refactor a bit
centralize KRB5CCNAME default handling

add kdestroy and kinit user clients
make the client name optional
remove my test realm
add a todo
fcntl is different on darwin.  make it work.