PIM-1606 : make date type readonly on attribute edit view
PIM-1606 : export date_type in attribute export
PIM-1606 : update attribute export scenario
PIM-1606 : import date type
PIM-1606 : update attribute import scenario
Merge pull request #511 from akeneo/PIM-1606

[WIP] PIM-1606 add date_type in attribute import/export