Refs #2567: replace footer icons with gray ones
Refs #2567: add path to Osha logo inside header
Refs #2567: refactor HTML and CSS for newsletter footer
Refs #2567: footer: add font-family Arial, center the text on last cell
Refs #2567: pink-underlined link for Osha website in footer; fix footer URLs, except for Unsubscribe
Refs #2567: increase distance between social icons in footer
Merge pull request #162 from sandriu/2567_newsletter_all

Refs #2567: refactor HTML, CSS and icons for newsletter footer