Implement content manageable footer links

[desigonz]

Acceptance criteria

• [ ] Design matches mocks
• [ ] This page is accessed by new nav node "Footer" in the left nav (last in the list).
• [ ] Ability to add footer links
  • [ ] User can user a page picker to select footer links
  • [ ] Display all pages in page picker
  • [ ] Adding a link will publish out the link at the bottom of the footer (site-wide)
  • [ ] By default, if author doesn't add a link name, the page name will appear in the footer
    • [ ] When using the website in English, the link pulls in the English title
    • [ ] When using the website in Spanish, the link pulls in the Spanish title
  • [ ] Alternate title: Author can optionally add a "Alternate title" to display in the footer of Janis (for example, the page Privacy policy for Austin.gov will appear as a shortened "Privacy policy" if that link name is specific in this field in Joplin). This field is should be translatable.
  • [ ] Arrows allow user to change the order that the links display from left to right (the topmost link in Joplin will display leftmost in Janis)
  • [ ] Limit to six; after six links are added, the "add link" button will no longer display.
• [ ] Ability to manage social media
  • [ ] Authors have options to add social media links for:
  • [ ] Facebook
  • [ ] Instagram
  • [ ] Linkedin
  • [ ] Twitter
  • [ ] YouTube
  • [ ] When an author deselects a social media link (via checkbox) and publishes page, the social media icon and hyperlink are removed from Janis.
• [ ] Unit tests: Will we need to write any unit tests for this content type or feature set?

[desigonz]

• [ ] Don't need SEO

[desigonz]

@briaguya For supporting drafts—does that change the size of this issue significantly? If not, I would say let's do it, and let's have the homepage be the preview page.