use "registration code" term everywhere

to be consistent with SCC terminology
Merge pull request #54 from yast/registration_CODE_term

use "registration code" term everywhere
"reg. key" -> "reg. code" also in non-ruby files
Merge pull request #55 from yast/registration_CODE_term

"reg. key" -> "reg. code" also in non-ruby files
removed FATE#316796 placeholder (feature dropped)
use suse-connect gem instead of scc_api
changes

- 3.1.38
better test description
Merge pull request #56 from yast/connect_gem

Use suse-connect gem as the backend (instead of scc_api gem)
upgrade: copy the old NCC/SCC credentials
register the base product using the old credentials during upgrade