Added Support for Relationships on NSManagedObjects

[hirad]

If you have two entities, both of whose classes conform to TGFoundryObject, you can have related objects created automatically when you create instances of one.

Tests and docs updated accordingly, as well.

[ehlersd]

@hirad Would you mind opening this same PR against my fork (since this repo seems to be unmaintained)? I want to add support for NON-CoreData relations as well, and would like to integrate your CoreData changes and follow the same process.

https://github.com/DoubleNode/Foundry

[yas375]

@ehlersd you don't need a PR on your fork to do that.

git remote add hirad https://github.com/hirad/Foundry.git
git fetch hirad

And then you can merge (git merge hirad/master) or cherry-pick these commits:

git cherry-pick 476fd38
git cherry-pick f3d079d

[ehlersd]

@yas375 Thanks! That worked great.

[hirad]

@ehlersd Great to hear there is an active fork. This PR was a bit of a hail-mary in case people who needed this functionality would see it here ;)

[ehlersd]

@hirad I'm not currently using CoreData in this project, but I do want to improve the way it deals with nested non-CoreData objects.

I also plan to add Realm.io object support as well. Any and all PR's are welcomed to advance this forward.