Issues 20 & 21: Add secondary featured posts, blog and sidebar along with widgets.

[delawski]

@kopepasah @ThierryA Please review this set of changes.

This PR adds styling and/or markup of the following elements:

• the secondary featured posts (right after featured post on the homepage)
• the article stream (used on homepage, archive, category etc.)
• the sidebar (used on homepage, archive, category etc.)
• the set of default WordPress widgets, i.e.:
  • meta,
  • recent comments,
  • recent entries,
  • RSS,
  • audio (needs markup adjustments in the BE to pass AMP validation),
  • video (needs markup adjustments in the BE to pass AMP validation),
  • search (needs markup adjustments in the BE to pass AMP validation),
  • the 'categories' widget is implemented partially, since it's not possible to implement redirect on select box change event
  • for the same reason as above, the 'archive' widget could not be implemented at all,
  • the 'tag cloud' widget needs a complete BE solution.
    I've left dev notes in the templates needing BE support.

[ThierryA]

@delawski fantastic work on this! LGTM

[ThierryA]

@kopepasah I believe this can move onto BE implementation once your CR is done. Since it is late for @delawski, I would suggest to apply to final touch to make sure it validates and merge this 👍

[kopepasah]

@delawski this looks good to me and thanks for leaving the dev notes regarding the redirects for the widgets.

[kopepasah]

@ThierryA good to merge into develop.

[kienstra]

Notice Of Other PR

Hi @kopepasah,
Plugin PR #870 involves adding support to native WordPress widgets. Have you begun implementing the widget templates here?

[kopepasah]

@kienstra this PR just covers the frontend markup for the widgets. Nothing is in the dynamic templates as of yet.