Validate range

[minimav]

This implements the validation on the Range param suggested in #698. I tried to match what I could see in other params which had such logic already. A couple of minor things:

• 'q's in the order error message for a named param was a compromise since %r's results in 'q''s which looks a bit awkward.
• The order error message could perhaps be tweaked to Range bounds... when validating the bounds rather than Range parameter ... for both bounds and the param value.

Fixes #698

[maximlt]

Thanks @minimav for this well appreciated PR! I have left one inline comment, otherwise it looks good, and I am very pleased that you made the effort to add some tests 👍

[minimav]

Thanks @maximlt, I have been a little busy and didn't manage to make the change you suggested.

[jbednar]

Looks great, thanks!!

[philippjfr]

Looks good, let's get this merged!

[maximlt]

Yep let me have a last look and merge after that.

[maximlt]

Thanks a lot for your contribution @minimav ! This fix is going to be included in the release of Param 2.0.