Improve Example Table display of whitespace strings #262

Hi Guys, great tool, I've been using this via Specify for a little while now and I've noticed what I think might be considered a mild usability bug or improvement with the display of whitespace and empty strings in the example tables in reports (this was pointed out by my PM).

Currently if I do a typical argument test with a set of null , empty and whitespace example strings as a parameter we would see the following:

• some string (just to show normal string behaviour)
• 'null'

This means there's no simple way to differentiate between an empty string and whitespace examples.

I would propose that it if the type is string, it does a quick check for an empty string, or whitespace and if-so wraps in single quotes, then you would read it as:

• some string (again, just to show normal string behaviour)
• 'null'
• ''
• ' '

This way you clearly see the difference in the examples. I've implemented this locally but I wanted to know your thoughts on this change before I raise a PR in-case you have some changes or ideas. Thanks.