Avoid calling recolorRows() for each closed node in a tree_editor.

Together with a slowness probably due to recent update to jquery, this
resulted in terrible page tree rendering times (around 40s for 400 pages).
Instead of simulating a click on the row, just call the row handler directly
and recolor everything afterwards.
Also speed up recolorRows() x5 by rearranging and caching some selector results.
Merge remote-tracking branch 'mjl/next' into next

* mjl/next:
  Avoid calling recolorRows() for each closed node in a tree_editor.