Repeated VirtualFiles and embedded data don't play well together

[YPares]

For now, if an optionsVirtualFile is repeated (e.g if it is accessed in a task repeated via FoldA or parMapTask), the options will appear only once in the config file. What we would like instead is to have that field in the config file be a JSON object, where the record of options will be also repeated and indexed by the TRIndex value.

This should also work for any embeddable VirtualFile (those who support serialization/deserialization to/from JSON). For instance, in example1 this would allow to directly embed the users data in the config file.