Feature changes:
- #405: add UserSetting for book stats sample size.
There was a big refactor/rewrite of much of the book stats
calculation code. The calculation isn't instantaneous,
but as the graphs are ajaxed in now, it should suffice.
Tweaks:
- Show term popup if parent is set.
- Ajax in book stats on home page for speed.
- Simplify datatables rendering.
Fixes: