Add knockout-es5 plugin.  Replace knockout module with a shim module that loads both knockout and the plugin together.
Start migrating the widgets to ES5 properties and ES5 knockout observables.
Ongoing widget cleanup

1. Change all non-viewModel widget getter/setters to be ECMAScript 5 properties instead.
2. Update specs and Sandcastle examples so everything is working again.
Ongoing widget cleanup

Partially port HomeButton and SceneModePicker to the new ES5 based convention.
Adjust documentation.
Ongoing widget cleanup.
Update documentation.
Ongoing widget refactoring.
Update clockViewModel
Make CesiumViewerWidger and BaseLayerPicker work again.
Port remaining widget code to ES5 properties.
Update CHANGES.md
More documentation cleanup.  Remove ImageryProviderViewModel.fromConstants.
Add licensing.
Fix trailing comma
Update ES5-shim library for running tests in IE.
Add a defineProperties helper method so the code still evaluates in IE.
Merge branch 'widgetCleanupES5' into widgetCleanup

Conflicts:
	Apps/CesiumViewer/CesiumViewer.js