RC2: Include resource type name in resource

[csantero]

https://github.com/dgeb/json-api/blob/v1rc2/format/index.md#resource-objects-

A resource object MUST contain at least the following top-level members:

"id"
"type"

I hate the naming for this - my project has a bunch of models that have a property called Type. But I haven't seen anyone complain about it, so I guess I'm the one who has to change.

We do have to handle the possibility that someone's model has a property that would serialize as type, though. Either we can throw an exception, or we can transform the name somehow (like prepending an underscore).

[karlguillotte]

Actually, I would like to have this feature added, I need it on the client side ;) Not sure why they decided to pluralize it.

[SphtKr]

Ditto, I'm looking forward to being able to tell the difference. I've started experimenting with a polymorphic endpoint and so far JSONAPI.NET seems to handle them okay, for GET at least. Was worried about that...fingers crossed.

[csantero]

Implemented in #80. Will track reserved attribute name collisions in another issue.