Update source and online documentation of silt fraction

[anne-glerum]

This PR updates the online documentation and the comments in Fastscape_api.f90 to

• use the term 'silt fraction' instead of 'sand-shale ratio'.
• replace 'shale' by 'silt'.
• switch the online description of the order of sand and silt variables in the FastScape_Set_Marine_Parameters function.

These changes unify the terminology with that used in Marine.f90 and the paper by Yuan et al. (2019) in EPSL. The order of the FastScape_Set_Marine_Parameters arguments in the manual is now also in agreement with the order specified in lines 43-52 of FastScape_api.f90.

Only in Strati.f90 is Sand/ShaleRatio still used as output parameter name (line 62); I didn't change it because it actually changes the output, not just the documentation. Let me know if I should also change that parameter name.

FYI @Djneu

[benbovy]

Many thanks for the feedback and for taking care of this @anne-glerum.

Only in Strati.f90 is Sand/ShaleRatio still used as output parameter name (line 62); I didn't change it because it actually changes the output, not just the documentation. Let me know if I should also change that parameter name.

I think the improved consistency would be worth the small breaking change here.

Note for myself: I'll need to update the marine component in https://github.com/fastscape-lem/fastscape accordingly.

[anne-glerum]

Many thanks for the feedback and for taking care of this @anne-glerum.

You're welcome!

I think the improved consistency would be worth the small breaking change here.
Okay, I've updated the output name as well.

It seems my git or vi has also unintentionally changed the EOL of FastScape_api.f90. I'm trying to undo that, unsuccessfully so far.

Do I need to worry about the failing testers? I don't think that changing the comments could cause these errors.

[benbovy]

Do I need to worry about the failing testers? I don't think that changing the comments could cause these errors.

You can safely ignore them, they are unrelated to the changes here and they have been fixed in #56.

[benbovy]

Thanks again @anne-glerum!