Restructure the examples in the documentation

[odow]

Because @bernardokp keeps banging on about it.

I don't have any immediate plans to do this because I'd prefer people focused on the tutorials which are more fleshed out.

But PRs accepted from anyone interested.

The examples are https://github.com/odow/SDDP.jl/tree/master/docs/src/examples

[odow]

As one example of a potential improvement

[Thuener]

What is the goal?
Change the formulation? Add this information to the page? Show the optimal values? Create an new tutorial?

[bernardokp]

Hello Thuener,

in this particular case, add the information to the page and show the optimal solution and optimal values.

[Thuener]

@bernardokp please check #801