Add support for touch events to SC.PopupButtonView

This simply map the touchStart and touchEnd events to the mouseDown and
mouseUp methods.
I'm not sure this is testable.
SC.MenuItemView: Add a right arrow when a subMenu is defined
Miss that there was already a has-branch element
FIx the FlowedLayout. Replace the "childViews" observer by another one on "childViews.[]". This was necessary because when adding children to the FlowedLayout, the added children were not positioned correctly (the observer not being triggered).
Restore _scfl_childViewsDidChange for backward compatibility.
Fixes regression in TreeItemObserver for determining indexes in sub-observer children.
Chrome has gotten uppity about using evt.returnValue, throwing a deprecation warning, so this gates the use of it to instances when evt.preventDefault is not found (IE8 and lower, see http://msdn.microsoft.com/en-us/library/ff975967).
Improves the delegate and item handling of SC.TreeItemObserver. Includes unit tests.
Moves SC.View#animate's adjust-on-zero-duration call to the next runloop.

All animations begin after the end of the current runloop; zero-duration animations should be no different, even if we're using the underlying adjust code instead.
Adds some documentation to TreeItemObserver explaining what will and won't get observed in tree-data-type terms.
Fixes regression that prevents developers from setting IDs the usual way.
Add support to SC.Button for firing the action on keydown.
Add constant for the delay value.
Fixes a regression where tree item observers’ delegates were forced to specify treeItemChildrenKey and treeItemIsExpandedKey. If the delegate doesn’t provide these properties, the defaults are used.
Ensure text field hint line-height gets set correctly.

Call _fixupTextLayout when appending to the document and when hint is shown
so the right line-height is applied.

_fixupTextLayout is called from didCreateLayer, but at that point the hint
may be hidden and have an incorrect outerHeight().
Removes the redundant fix up text layout call from didCreateLayer.
Adds unit tests to verify the bug fixed by #1126 / #886. BOOM!
Merge pull request #926 from nicolasbadia/popup-touch

Add support for touch events to SC.PopupButtonView.
Removes unused test code
Implement missing key handling functions on SC.TextFieldView.

The switch to using interpretKeyEvents missed implementing
some necessary functions.