fixed upward infinite scrolling so that it is less jarring
fixed infinite scroller so that it takes the height of OP into account when detecting when to load more posts while scrolling up
closes https://github.com/NodeBB/NodeBB/issues/2126
oops - #2126
closes #2124
always pipe child output to parent
closes #2125
don't blow up nodebb if plugin.json is broken
filter:post.getPostSummaryByPids
forgot to return just posts array