[FEATURE] Updates for landing page

-Changed main hero graphic and welcome text
-Adjusted nav colors and subnav dropdown
-Removed icons from nav (mobile as well)
-Centered active ‘carat’ for main nav items
-Added links to gateways
-Updated to use ‘mixedCase’ for naming styles
-Removed <strong> tags from Jade and updated styles
-Removed unnecessary ‘ticker’ section
-Updated main logo to be a background image
-Changed @lightgray variable to match branding
-Code cleanup as per comments (2 spaces for indenting)