Refactors DisplayListTree class

removes item tree. flat displayobject store is sufficient.
Restores selection after update
Adds simple keyboard nav; optimized element creation
Remove duplicate listeners
Prevents default in displaylist's keydown handler
adds wireframe mode
restores display list scroll position
Use getBounds instead of _bbox
Do not clip invalid regions in wireframe mode
getRegion to return getBounds when in wireframe mode

unsure about this, seems to have undesirable side effects (ghost elements appear in wireframe mode). @tobeytailor, help? ;)
Visualize wireframe outline color in display list
cosmetics
prevent displaylist panel to show unnecessary scrollbar in firefox
removes some renderAsWireframe conditions
makes lint happy (missing semicolon)
Merge remote-tracking branch 'origin/master' into inspector

Conflicts:
	src/swf/renderer.js
Merge pull request #628 from claus/inspector

Inspector: Display list visualization and other feature requests - Wireframe mode