[netcdf-java] New authorization and credentialling mechanisms....

I have added the new authorization mechanisms
to the current netcdf-4.3 trunk
(github.com/Unidata/thredds).

The documentation is in the docs directory
or is also available as
http://www.unidata.ucar.edu/staff/dmh/Session.html

Comments desired.

=Dennis Heimbigner
 Unidata