Add a resources property to the Resource class

[jstano]

It's not clear how to get the _embedded stuff in the Hal renderer working without having a new property in the Resource class or having a class derived from Resource with a resources property.

If you can provide an example of how to accomplish this without any changes to the project, that might be helpful.

Here's what I'm proposing:
new Resource(someDTO)
.withResources(someCollectionOfResources)
.withResources(otherCollectionOfResources)

If no resources are added to the Resource, then nothing will be output by the renderers.

I'll create a Pull Request so we look over the code.

[gregturn]

Resolved via #864.