Removes canceled flag and dev warning when an invisible view is animated.

Note for future reference that although an adjusted-instantly animation was not cancelled, it wasn't run normally either, and we may want to come up with a way to alert callbacks to this.
Adds RootResponder support for browser data drag event.
Adds unit tests for RootResponder's data-drag events et al.
Adds documentation to SC.View for the new data-drag events, as well as mouse move, click, touch and keyboard events.
Makes SC.Pane#sendEvent's second (evt) argument optional.
Cleans whitespace.
Improves the tracing for statecharts by using console styling and indicating when states are entered by route or not.
Uses the console for debugging of observers since SC.Logger is not available for the SC.Observable mixin (SC.Logger extends SC.Object, which mixes in SC.Observable).
Removes double clone of observable members array. The `getMembers` function already does a slice of the array, so SC.clone (which just does another slice of the array) is unnecessary.
Cleans per jshint.
Prevents bindings that are disconnected at the moment of updating from continuing, which would throw an exception because the binding would try to resolve both sides of the connection and become connected to the window (which doesn’t support the KVC methods the binding uses).

One scenario that this has been seen in is an observer that destroys an old binding and creates a new binding to a *store query based computed property*.  As the binding is about to update, it first has to get the value of the query based computed property from the target, which results in the store flushing and indicating certain records did change which in turn triggers the original observer function where the binding is replaced. In the very next step, the old binding, which is now disconnected, tries to syncronize its value, which will fail.
Improves console trace formatting for long lists of before and after states.
Move drag code from SC.PalettePane to a mixin.

This moves the code that makes SC.PalettePane draggable into a SC.Draggable
mixin. This allows any pane to be made draggable.
Skip handling drag events on draggable panes if the target of the event
has indicated text should be selectable.
Renames draggable pane mixin. Tweaks documentation and comments to make it clear that we're not handling the edge case of panes which appendTo elements other than the body.
Fixes RootResponder data-drag unit test to conform to final design. Oops
Adds unit test showing that value changes don’t update the title or icon.
Fixes regression that the icon of the selected item doesn’t update the view.
Adds ability to set the value of the view and have the view’s title and icon update.
Fixes a bug where separator items gained the value of the previous item such that the separator item would appear selected in the menu when the previous item was actually selected.
Fixes an issue where custom transition plugins still call didTransitionIn/didTransitionOut even if a transition was cancelled.
Adds design modes support to SC.Pane, allowing the design of an application to very efficiently and easily change depending on the width of the display.

While a design may be flexible for a wide range of display widths, at a certain point it no longer makes sense to keep stretching or compressing views and instead it is better to completely alter the design.  A prime example is that a design that can flex between a medium sized display like a tablet and a large sized display like a desktop, will not likely work for a small display like a smartphone.  In order to very easily alter the design, SC.Pane provides the designModes property which includes the width thresholds that you want to trigger a change to the overall design of the application.  Each time a threshold width is crossed, the child views will be updated with the new design mode.  At this point, any properties dependent on 'designMode' will recompute allowing you to adjust settings such as isVisible.

As well, SC.View has a new property 'designLayouts' that is simply the layouts for the 'designModes' you define.  For example, if the design mode becomes 'small' any child view that has a 'small' designLayout will have its layout automatically set.

This completes work spec #843.