Update secondary pages look and feel

Now that our new look and feel is approved, we should focus on defining the look of our secondary pages.

Requirements:

• Define header and footer for secondary pages
• Define sub-headers (Blue section at the top of: https://iot.eclipse.org/getting-started/)
• Define default styles for standard HTML elements listed on https://www.eclipse.org/eclipse.org-common/themes/solstice/docs/typo.php