Enable longoptions support for grdproject.

[rbdavis]

Description of proposed changes

Python differences:

Changed -F scaling to one2one|one2one_scale.

Julia differences:

No differences.

Fixes #

Reminders

• Make sure that your code follows our style. Use the other functions/files as a basis.
• Add tests for new features or tests that would have caught the bug that you're fixing.
• Describe changes to function behavior and arguments in a comment below the function declaration.
• If adding new functionality, add a detailed description to the documentation and/or an example.

[remkos]

This may be very late in the game to ask, but I think we should be more flexible here, since it would be easy to forget the exact syntax. Can we do something like:
"cm,inch|in,point|pt,meter|m,foot|ft,km,smile|mi,nmile|nm,ussft"

I'm not sure that a single letter "m" would work. To be checked.
Also this should then be used consistently in other modules.

[remkos]

Similar to the above: could we do "cm,inch|in,point|pt"?

[PaulWessel]

I am not sure if we want distance units to be spelled out. That would mean hundred of places where we should allow km for k, point for p, etc, Think of map projections, e.g. Jm72point. I think it is cleaner that people need to know what the unit abbreviations are instead of having to deal with smile and foot. I think the most commonly used units will be c, i, p, m, k. Doubt anyone uses USGS survey foot. Mariners may use nautical miles.
However, I am happy to hear what more people think of this. Seems like unnecessary and much work to mel @joa-quim?, @seisman ?, @leouieda , @Esteban82 ?

[joa-quim]

Agree with no long names here. 250smile may look modern but is wrong (should be plural)

[PaulWessel]

Agree with no long names here. 250smile may look modern but is wrong (should be plural)

Tru for all of them, then: kms. Gets crazy as in science nobody would use plural unless spelling kilometers. They may write km in sentences but we dont want to go there. c,i,p,m,k,n,M,f,u is fine,

[remkos]

I was not intending to create such a big thing. But it is true that it would be confusing, since we stick to c,i,p etc. for units (as in -W1p,blue) but then use the units written out here in grdproject

So I agree with the consensus among @PaulWessel and @joa-quim to use "c,i,p,m,k,M,n,f,u " and "c,i,p" resp.