Update examples

[ckormanyos]

We can upgrade some of the examples, as partially motivated by discussion in #718.

• Having one example that demonstrates the using trick when necessary, would be good.
• The Jahnke-Emden-Lambda example makes use of using. But we could emphasize it even more.
• The Calculating a Derivative example could make much better use of using, particularly in the calls of the derivative functor(s).
• The Calculating an Integral example could be made much more generic. It seems to already be relying on ADL and does not use using. I'm not even sure it is set up properly for float, double or long double?
• Looking at Polynomial Evaluation I have evolved in the past 20 years or so. These days, I tend to prefer Pade-like expansions for these in order to reduce the coefficient list(s). These still require polynomial evaluation for the numerator and denominator in the Pade approximation.
• In the Gause-Laguerre example, we could post the full link to the Wolfram alpha code for the guess at the numbers of coefficients.