Try to use Conn
Export dns.Conn and make it more like net.Conn

Export lowlevel function and types so that they may be used.
They higher level Exchange function is still there. ExchangeConn
is gone, because it is not needed.
Remove xfr
More documentation
Some more changes.

Still pondering dns.Conn and a dns.Dial
Make TSIG work again

Start fixing and using the UDP bufsize option.
Fix timeouts, Tsig and EDNS0 update size
Update all the tests
Some test tweaking
Add Timeouts back in.

Fix the timeouts
correct documentation
doc updates
Remove long deprecated functions too
Rework the transfers stuff
Partial changes for xfr
More transfer stuff
Fix transfer
make these methods privates
Fix xfr some more
More xfr fixes, does not work yet