Ownership guide

This is a work in progress, but this should get *extensive* review, so I'm putting it up early and often.

This is the start of a draft of the new 'ownership guide,' which explains ownership, borrowing, etc. I'm feeling better about this framing than last time's, but we'll see.
Where is the place to argue about it?

Also, the real reason it annoys me is that it is illogical, and inconsistent. You have 'ownership,' but not `Box<int>.` No, you have `Box<int>`, which is the much more logical case; therefore, 'ownership', to keep it consistent.