Replace non-ASCII characters by ASCII characters in the names of variables, structs, functions and macros

[CFBaptista]

Issue addressed

Fixes #352

Explanation

For improved code readability it is now discouraged to use non-ASCII characters for naming variables, structs, functions and macros. Using the non-ASCII character for built-in operators is still allowed. This change in naming convention is now in effect and all invalid uses of non-ASCII characters have been replaced by ASCII equivalents.

Checklist

• Updated tests or added new tests
• Branch is up to date with master
• Tests & pre-commit hooks pass
• Updated documentation if needed
• Updated changelog.md if needed

[verseve]

Thanks for these changes. I did make some suggestions for changes in the code (did not mark these in the docs, of course some changes also affect the doc files).

[JoostBuitink]

Thanks for all of these changes, LGTM! I have only two small comments.

I decided to explore whether it is possible to change the (many) beta's into more descriptive names, but most of these originate in the kinematic wave equations, where they are originally also described as a \beta (without a real meaning, other than being a constant). So I think it is best to stay close to these equations. Some are in the flextopo and HBV concepts, where I believe it is also best to keep them as they are. What do you think @verseve?

[verseve]

So I think it is best to stay close to these equations. Some are in the flextopo and HBV concepts, where I believe it is also best to keep them as they are. What do you think @verseve?

Yes, I think for now it is best to keep these variable names as they are. If we want to change this (also my comment in Teams about variable name consistency) we can work on this as part of another issue/PR.