Actual use of language parameter in the content definition screen in the case of JSON content format

[#1]

Currently the language parameter in the content definition screen is not of any use. It is not possible to have more than one content per Offer per Placement, even if they are in a different language. So content differentiation on language needs to be done through if statements in the same single JSON per Placement. It should be possible to define a content per Placement per language.

We need to have the same content always in two languages, Dutch and French. It would be most logic to be able to indicate in the language parameter in which language the content is defined. Now this language parameter is not of any use in the content definition screen. Adding the possibility to define a content per Placement per language would also simplify the JSON definition of the content because additional if statements can be avoided.