remove next and previous functionality from router
remove #next and #previous from posts_controller
remove #next_post_path and #previous_post_path from postpresenter
remove PostViewerNav
remove PostViewerAuthor
remove PostViewer
remove PostViewerInteractions
remove PostViewerFeedback
remove template picker functionality
remove template picker
remove useless specs
remove wallpaper-mood template
remove old styles
bump sidekiq
remove old templates
move everything under post-viewer/ to single-post-viewer/
add changelog entry
Merge pull request #4612 from diaspora/drop_spv_old_code

 Drop spv old code
Add indication about markdown formatting in the publisher
Add expand the publisher test