Fixed bugs in attribute._getAttrCfg and state.removeAll, found while bumping up unit test coverage for attribute-extras and attribute-core. Fixes #2531891. Fixes #2531892 Added standalone state unit tests also.

Broke up Y.Attribute into: Y.AttributeCore (Attribute without Events, or lesser used features) Y.AttributeEvents (AttributeEvent support) Y.AttributeExtras (Attribute lesser used features) Y.Attribute remains 100% backwards compatible. Attribute/Base/Widget/Plugin/App/Node/WidgetParentChild tests all pass. Y.State's internal data structure was changed. If you're accessing the private _state.data's fields directly, you'll need to change code. HISTORY.md has details.

Cleaned up API docs for Attribute/State. Also more API doc tweaks for Base. No code change (-min unchanged)

Split State.remove into State.remove, State.removeAll. Updated Attribute/Base READMEs, and filled in missing API docs

Attribute/Base performance tweaks. Attribute - avoid event publish/event fire on initial set : 85% improvement in construction times in FF3/Win. All attribute tests and DD/Anim/Overlay/Slider examples pass. State - added methods to add single properties to avoid object literal creation for single properties. Minor loop, if/else refactors

Performance tweaks - Reuse attr change event publish config object, Reuse facade mixin literal when possible, Avoid republishing already published attr change events, Avoid each in State.add iteration, just because its on critical path

First Attribute pass on beta1 candidate - still have an issue to fix with static object values

Directory re-org - widget, widget-stack, widget-position, widget-position-ext, widget-stdmod, overlay, attribute, base, json