Fixed call to invalid method from Model class
Regular user could not add a product if there was none in the table
Fixed invalid SQL query
Added support for list->sorting->filter in DC_ProductData
Use list->sorting->filter instead of "root" to filter products
IsotopeBackend::getAllowedProductIds will return new statuses

- boolean true = everything is allowed
- boolean false = nothing is allowed (no permission on product types or groups)
- array = products found (can be empty)
Allow getAllowedProductIds hook to deny access to any products
Invoices should be created in the user's language (#524)
CS
Fixed missing angle bracket in MediaManager
Do not allow to add the same image to fallback and language record
Remove images from language if removed in fallback (#465)
Hide language option if there is just one language in the page tree
Added new attributes option to fetch fallback data

When field -> attributes -> fetch_fallback equals true, the query
statement for fetching a product will include the fallback languages
in "field_fallback" result set.
Merge media data from fallback language (#465)
Release 1.4.rc2
Merge branch release/1.4.0 into develop