Updated to work with Puppet 3.x `puppet cert` command
Default to not adding host entries.
Fixed path to cobbler preseed files
Don't default to an empty password.
Parameterized preseed template & late_command
Reworked cobbler node registration

* A shell script is generated for each node that contains the cobbler
  commands to add or update the node.  Puppet will run this script when
  it changes.

* Changed reference to `cobber_sync.py` to run `cobbler sync` instead,
  so that the python script doesn't overwrite our systems we've
  registered outside of cobbler.yaml