New ownership guide

This is the start of the new "Ownership" guide, to replace the lifetimes guide.

I'm still working on it, but I wanted to share my progress, as this guide is _very_ important, and I'd like as many eyes on it as possible. :smile: 
Ah, you are right. I'm sorry. ("This code can be compiled":  373,000 hits, "This code compiles": 620,000 hits on Google)
> The compiler compiles. The programmer programs.

Definitely.