Adds Percent service decorator to increse/decrease costs by a percentage
Renames Percent decorator to Reduction and adapts calculation
Implements delivery/payment option update when the basket content changes
Changes config value from "percentage" to "percent" in Reduction decorator
Fixes price calculation in ServiceUpdate plugin
Shows always the price for delivery options in list
Adds Reduction decorator to demo data
Fixes naming in backend config
Merge pull request #606 from nsendetzky/master

Implements service costs reduction decorator and service update plugin