Adding an outline or SymbolProvider

[isometimescode]

I have a version of an outline using headers and the nested header. This is what it looks like on the bean-example data, with warnings and errors displaying on the side:

This is similar to the outline noted in #64, and I had attempted another one for #25, but I don't use ;#region folding as much as I use nested * and ** for the headers.

I'm happy to submit a PR either way, depending on what other users need.

[tcpekin]

I have installed this from your repo and it works great so far!

[Lencerf]

Merged. Thanks!