The product list can now automatically mark and optionally filter for new products (#418)
Removed functionality from front end module
Can now set the days to mark a product as "new" in shop config
Moved functionality to product class
Can now also display only the "old" products
Removed useless variable
Use timePeriod widget to define "new period" of products
Do not modify "model" properties
Use time period to determine isNew() on product
Add "new" class to product list, reader and collection
Fixed database field names
Serialized field is bigger than int ;-)
Improved DCA for newFilter field
Consider new product filter in the product list cache
Delete product cache when changing store config

Product availability could be changed (e.g. "new" products)
Do not retain dateAdded when duplicating a product
Rewrite "new products" filter using SQL query
Define SQL fields in DCA
Merge branch 'feature/mark-new-products' into develop