treedrawing.css: fix the height of context menu cols

fixes #4

Note that we lose the rules between columns with this fix.  If we want
them back, we’ll have to look at:
http://matthewjamestaylor.com/blog/equal-height-columns-cross-browser-css-no-hacks

(CSS is insane.)
treedrawing.utils.js: overhaul case functions

Split them into fns that work on label strings, and those that work on
nodes.

We need this for the following change, which addresses case in the
context menu.
treedrawing.contextMenu.js: interaction of case and menu

Two changes:

1) Allow N-A (noun accusative) to show the proper dash tags for a plain
   N in the context menu

2) Add -A to all these dash tags