Better rules for default value of DTOs' attributes

[Gabriel-Darbord]

When exporting DTOs' attributes with a default value, we can try to transpile it.
Primitives were considered an easy case, however not all of them can be rewritten as-is. For example long litterals are suffixed by L in Java, however this notation doesn't exist in JavaScript. With this particular example we might consider using BigInts.
We refused to transpile instantiations, but we could make an exception when the instanciated class is the DTO itself. This can happen with user-defined enumerations.