Reduce CSS specificity for Link Styles

[CITguy]

Update instances of a[href] (011 specificity) to :link (010 specificity) in LESS/CSS.

• https://github.com/rackerlabs/helix-ui/search?l=Less&q=a%5Bhref%5D
• caniuse :link compatibility
• MDN :link browser compatibility

Categorized as Bug: CSS due to increased complexity required to override in consuming apps.

[CITguy]

After a brief attempt, I discovered that :link:visited is not equivalent to a:visited. Will need to investigate further.