CSS Twerks

Un-uglifying the required/invalid input state (now uses red border and
font awesome icon)
Adjusting x-panel table header hue (to $darkNeutral)
removing legacy green buttons in package manager (now $primary)
retina-tizing x-btn-split (Download Extras button)
uberbar result hovers (%nav-item)
Help Page Improvements

Retina CSS MODX Help Logo
Primary Action styling on sign up button
Merge remote-tracking branch 'origin/pr/696' into develop

* origin/pr/696:
  Help Page Improvements
  CSS Twerks