Fix TreeView for subtrees in Audit widget

* Handle case where `display()` is called before controller element is
  added to DOM
* Explicitly call `display()` on subtrees when they may be re-rendered
  due to live binding (mostly subtrees in `Request`, `Response`)
Merge pull request #1173 from reciprocity/feature/fix-tree-redisplay

Fix TreeView for subtrees in Audit widget