sort displayed addons (bnc#888567)
use the custom URL also in upgrade (bnc#894592)
added some logging, continue after registring the system
avoid SLP discovery if the default SCC server was already used for registration
added exceptions_spec.rb test
addon sorter - better handle nil or empty product_type value
added missing require in Autoyast client (bnc#895147)
changes
Merge pull request #157 from yast/sort_addons

Sort displayed addons (bnc#888567)