split up price update into price update and price history, to not mix up two diffeent things
refactored amazon set price
removed unnecessary function from api helper
adjusted script for use with new db-scheme
added correct display of old price / new price field
added correct display for change price
fixed error due to variable renaming
added manual execute button
added isChangePending field to return value of setPrice to be evaluated by js later
changed js to use isChangePending instead of Written
Merge branch 'feature/RefactorPriceUpdate' into develop