Merge remote branch 'upstream/master'
Add basic layers support
Add support to add/remove layers and change their levels.
Add layer-level-changed event and add $.indexOf polyfill
Fix $.indexOf pollyfill
Add the original options in addLayer events
Add layers demo page
Uncomment version
Add viewer.getNumberOfLayers method
layers.html test file:
-display 2 layers after opening
-fix order
-add opacity demo
-add rotation demo
Add viewer.getLayerAtLevel method and rename getLayerLevel to getLevelOfLayer.
Add layers unit test.
Prevent adding collections as layers.
Throw an error when trying to add a layer in collection mode.
Allow base layer reassignment if not in sequence mode.
Support removal of base layer.
Remove not working code
Move all overlay code from drawer to viewer
Add layersAspectRatioEpsilon check
Update the source when the base layer change.
Fix crash when closing the viewer when no overlay has been added.
Fix doc in point.js
Fix imageToViewerElementCoordinates method and corresponding unit tests.
Add overlays unit tests