small lib/ refactoring
handle pkg-bindings errors
move SW management functions to separate file

(to lib/registration/sw_mgmt.rb)
move language function to a separate file
use WFM.GetLanguage for getting the current language

(removed yast2-country dependency)
update Makefile.am
rename "selected_base_products" -> "products_to_register"

to better match the functionality
import fixes
added missing textdomain
changes

- 3.1.13
code review fixes
Merge pull request #19 from yast/check_pkg_errors

Check pkg errors