display SSL error from exception (bnc#882573)

- hide details section if there are no details actually
changes
Merge pull request #108 from yast/ssl_error_details_fix

SSL error details fix
fix version provided for the extension list
added changes
Merge pull request #107 from yast/master-mc-fix-product-version

fix version provided for the extension list
do not log the registration code
changes
Merge pull request #109 from yast/do_not_log_reg_code

Do not log reg code
use the new connect SSL API

(see https://github.com/SUSE/connect/pull/115)
changes
Merge pull request #110 from yast/new_ssl_API

New SSL API
properly mark the registered addons

to display correct status when going back in the installation workflow
use new line as a separator in error message

product name might be too long to fit a single line
allow adding extensions for already registered extensions

fixes the problem that HAGEO cannot be selected after registering
HA only and then going back
changes
move the code to model

- added tests
tests - better test descriptions
Merge pull request #111 from yast/mark_registered_addons

Mark registered/selected addons when going back
added a popup for changing the registration server URL (bnc#883138)