This reverts commit 5717a9a7

Issue #3083877 by agami4: Update hero for the group pages, complementary merged block, secondaty nav

Issue #3083877 by agami4: Update group page, add styles and script for secondary nav on the profile and group pages

* DS-4632 by left: add overlay with gradient to hero element, wrap intro content in blockquote, styls to reflect, vertical align hero content on mobile

* DS-4632 by left: tweak activity overview icon and font style, align both columns, always wrap main block in primary div for max width of 2/3, align readmore by adding primary selector

* DS-4632 by left: teaser background on image wrapper from grey to brand primary

* DS-4632 by left: replace topic icon, add landing page icon, gulp sprite-icons

* DS-4632 by left: edit reference to icon for user in activity overrview, remove fine control rule for topic icon

* DS-4632 by left: add icon to landing page teaser template, change bg colour of teaser image wrapper

* DS-4632 by left: delete preview css, mistakenly generated

* DS-4632 by left: reset teaser image wrapper to grey background

* DS-4632 by left: replace topic icon, generate icon sprite

* DS-4632 by left: replace topic icon, generate icon sprite

* DS-4632 and 4791 by left: add conditional for teaser image in templates, if no teaser image add hr

* DS-4632 and 4791 by left: add hr style for no teaser image

* DS-4632 by left: replace topic icon, generate icon sprite

* DS-4632 by left: add featured viewmode to viewmode array in node preprocess function to use same date format on featured items as teasers