Back porting a couple of live changes

Asset version number and image display sizing for the popular posts bar.
Fixed popular posts query

Now returns actual sensible results rather than conflating the two
aggregate columns and also considering spam comments
Updated Elastic and Bootstrap via composer
"View post" button in manager
Tumblr theme fixes
Search box visual fix
Fix post extra persisting on post create

Now basically blanks the extra array before initially persisting, then
set them back once the post has an ID
Stop link descriptions being madnatory
Search / filter for links in manager