Create and impose some code standard

[danielhollas]

We should make at least some basic rules and try to stick to them.

For white-space, we could use e.g. this:
https://github.com/pseewald/fprettify

See also: http://fortranwiki.org/fortran/show/Tools

[danielhollas]

We should do this as the last commit of 2.1 release and AFTER merging all current branches.

[danielhollas]

Here's a neat trick for ignoring huge formatting commits in git-blame

https://www.moxio.com/blog/43/ignoring-bulk-change-commits-with-git-blame

And here's one example from Discourse
https://github.com/discourse/discourse/blob/c61ebc9ba67d6588c09c2b93205865e0fd388f51/.git-blame-ignore-revs

[danielhollas]

We will use fprettify for this, though it's capabilities are fairly limited. We should also add fprettify workflow to CI.

We should also be using -Wall compiler option and use GFortran as the de-facto linter.

[danielhollas]

There have been a new release of fprettify, which is very encouraging! Some of the new functionality will likely be very useful.

https://github.com/pseewald/fprettify/releases/tag/v0.3.7