Merge workspace and social collaboration folder types

A workspace is a collaborative folder by default. It might have a "social" configuration or not, but it is a collaborative folder.

The social collaborative workspaces are confusing: it means that the other workspaces are not collaborative, which is not the case.

To make the rights clear for all, we have to use standard Workspaces and improve them with relevant social features from Social Workspaces (and deprecate them).