Wrap grdsample

[willschlitzer]

This pull requests wraps the GMT module grdsample.

Fixes #1422

Reminders

• Run make format and make check to make sure the code follows the style guide.
• Add tests for new features or tests that would have caught the bug that you're fixing.
• Add new public functions/methods/classes to doc/api/index.rst.
• Write detailed docstrings for all functions/methods.
• If adding new functionality, add an example to docstrings or tutorials.

Slash Commands

You can write slash commands (/command) in the first line of a comment to perform
specific operations. Supported slash commands are:

• /format: automatically format and lint the code
• /test-gmt-dev: run full tests on the latest GMT development version

[weiji14]

Thanks @willschlitzer! Just a few suggestions regarding the use of common aliases.

[weiji14]

Looks good to me. But please hold off on merging until we decide on whether we want a PyGMT v0.4.1 release, or go straight to v0.5.0 as discussed in #1356 (comment)

[weiji14]

Thanks for your patience @willschlitzer, now that the v0.4.1 tag is behind, we can finally finish this PR (and all the other ones you have lined up). Could you please resolve the conflict on decorators.py and fix one tiny issue I suggested below?

[willschlitzer]

@weiji14 I made the changes you suggested

[michaelgrund]

Fine to merge after the suggestions by @seisman are implemented!

[seisman]

It seems other modules (e.g., grdfilter) use the alias spacing rather than increment. We should keep the alias consistent, no?

[weiji14]

🚀