Move document dependent data out of header section

[RigoLigoRLC]

Document dependent data could come in multiple ways; Net manager returns a string object while net class is deserialized through deserializer (which output pointer to dynamically allocated string).

Putting them into the header will result in the situation where we must concatenate everything, which causes a lot of unneeded copying.

There should be a function in the deserializer which returns a vector of pointers pointing to strings on heap. Then Core will ba able to output them without having to concatenating everything again. This also requires the return type of data should be unified (all should be pointers to strings on heap).

[RigoLigoRLC]

Why nets are not going through deserializer? because nets needed to be converted while serializing. So we have the net manager to do it. And we integrated the deserializing functionality into the manager, which seems okay. But netclasses doesn't need such conversion so serializer literally puts the data into the list of netclasses accordingly.

Obviously this is a behavior we should unify.