added BaseLayerPicker capability to receive an array of providers
and to accept ImageLayers as well as providers
added destroy function to Timeline
cosmetic changes as per Matthew Amato's code review
see https://github.com/AnalyticalGraphicsInc/cesium/pull/798
Merge branch 'master' of https://github.com/AnalyticalGraphicsInc/cesium

Conflicts:
	Source/Widgets/BaseLayerPicker/BaseLayerPickerViewModel.js
	Source/Widgets/Timeline/Timeline.js
Merge ../cesium-akos NOT FUNCTIONAL Read on

There is a merge conflict in
Source/Widgets/BaseLayerPicker/BaseLayerPickerViewModel.js

Search for the string ">>>>" to find it
When it is resolved we will have updated OAM to the latest
cesium.

Conflicts:
	Source/Widgets/BaseLayerPicker/BaseLayerPickerViewModel.js