switch microblog feed to sopml:url
river collapse pref support
add river collapse pref to database
version++
style support for river threads
river template subitem parsing for threads
subitems need ids so we can un-sticky them in concert with the parent
but only if it's really sticky
use id, not data-id
put the parent id in as a class to make things easier
when you un-sticky a parent, the sticky subitems should un-sticky also
build_river_json2() builds the threaded river
rebuild rivers every 2 minutes