server returns action after executing it, so plesk_id etc can be accessed
remove return value from actions. expose attributes via readers
add listing of service plans
use ox for xml parsing (it is much faster)
add ox and builder to the gemspec
remove require of the complete plesk_lib from gemspec
add owner filtering for customer listing
remove unused find_service_plan.rb
remove dead code from service plan
add subscription listing
add support for creating subscriptions