Add FPVgen to affiliated packages

[MatthewBonanni]

Using the new two-point temperature control capability of Cantera 3.1, I built a tool called FPVgen, which automates the calculation of flamelet progress variable (FPV) tables with a simple input file and single command. I think others in the combustion LES community may find it useful. It computes the full S-curve, with an implementation based on this example: unstable branch. It automatically assembles a table from the resulting data. This table is built and exported in the format relevant to our lab's LES code but this could be easily extended to other formats.

Name: FPVgen
Description: automated flamelet progress variable (FPV) table assembly tool
Repository: https://github.com/IhmeGroup/FPVgen
Maintainer(s): Matthew Bonanni

[bryanwweber]

Please feel free to make a pull request to add this. Thank you for using Cantera!

[speth]

Let's hold off this until #263 is merged -- there's a major reorg in there that transfers the contents of affiliated.rst to affiliated.md in a different location and we'd lose this in the process.