Fixed bug when rows have non-constant height (drawing now positions itself absolutely relative to the page, should be pretty robust, though I admit it's hard to read).
Expression editor is disabled unless the signal is in expression mode. Also took out some debugging helpers.
Remove delay for redrawing arrows (affects scrolling), doesn't seem to noticeably slow down operation (if update_display() is limited, redrawing arrows will only be called so often anyway).
  Added a few css rules to keep status bars from expanding.
Added a shift handler for selecting multiple rows
Merge remote-tracking branch 'aaron/master'