Make links behave more like PatternFly

Particularly the underline text decoration only appears during the mouseOver event.

Note: Due to the following oversight/bug we have to use a border:

https://github.com/mdgriffith/elm-ui/issues/158

How to Test

Make sure any links have underlines when you hover over them. See bread crumb and the About page for examples.

Screenshots

Before

exosphere-link-before

After

exosphere-link-after

QA Checklist

• Any changes to 'widgets' in src/Style/Widgets/? If so:
  • Update src/Style/StyleGuide.elm showing example usage of that widget
• Were any app flags created, modified, or removed? If so:
  • Update config.js and all files in environment-configs/, including docker-config.js
  • Update "Runtime configuration options" documentation in README.md

Post-Merge Checklist

• Create follow-up issues for anything left over for another merge request
  • If any technical debt is introduced, assign these follow-up issues to the MR submitter