added price update db-sheme
added getCurrentPriceDataByReferrer to api helper
added setPrice functionality to amazon api
added api route and json variant of setPrice
enabled webinterface to use amazon set price functionality
added possibility to restrain get amazon data to a specific item id
used sku as additional index for amazon data
minor improvents
added route exception handling to report unavailable routes with 404 error
implemented getPrice methods
use getPrice methods as route endpoints
Merge branch 'feature/AddAmazonPriceSetting' into develop