Revert "Render posts against the owner page rather than topic"
While implementing categories for Flow headers and topic
summaries, i realized that this means that all recorded
properties about a page must attach to the board, giving
no way to categorize or do anything else against a topic
Talked about this in standup, it seemed agreed that while
there are good points about this patch, it would be
confusing to have only categories apply to the topic and
other properties such as links attached to the board.
This reverts commit 2a6388a7ec98f16b977933139610f67a53170b5a.