Added methods and events for subnode, subview and layout add/remove.

Added constantlayout.
Added variablelayout.
Added shrinktofit.
Added alignlayout.
Added spacedlayout.
Added wrappinglayout.
Added resizelayout.

Fixed a few big issues that came up once I started adding/removing views after initialization. There is/was a problem with the scope for event binding which I worked around. Moved the subnodeAdded events to a time after all but the late attrs have been set so that wierd race issues will not occur.

Added in listener for parent init to improve performance regardless of when the layout is instantiated.