Settlement timing vignette needs more info

[e-perl-NOAA]

We should expand the settlement timing vignette with more practical information and examples of setup (in the various input files.

• Need to show how multiple settlement timings should mean that the user should put in multiple subseasons
• Where to add the parameter for settlement timings in the recruitment distribution parameter section for each settlement
• Verification in the numbers-at-age table at the settlement point

@Rick-Methot-NOAA will likely need your help with this. The manual just says to add a parameter, not what to put in those lines.