Wrap a few long lines in tree_editor.py
Fix occurrences of E501
The testsuite was already ugly before
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.