Network model generates IPv6 prefix by default or when set to auto (includes TESTS) [2/2]

Sledgehammer control.sh pings the IPv6 address during discovery,
this fails if there is no IPv6 prefix in the network.

The bootstrap code was not getting the prefix, so discovery was failing.

This code creates the prefix by default OR if you ask for "auto" in the field.

Added tests to make sure this is working AND that we create them by default
for the admin network.

Also, cosmetic menu cleanup.


 BDD/features/network.feature                       |   23 ++++++++++++++-
 .../barclamp_network/networks_controller.rb        |   14 +--------
 .../app/models/barclamp_network/network.rb         |   31 ++++++++++++++++----
 3 files changed, 48 insertions(+), 20 deletions(-)

Crowbar-Pull-ID: 7b2595345449549a947599bce19b7b2359708d68

Crowbar-Release: development