Added tab for layer list pane
Added layer list.
Added opacity slider.
Added sublayer list

Does not yet function.
Checkboxes are now checked when they should be.
Added functionality to apply button

ArcGISTiledMapServiceLayers no longer have sublayer checkboxes.
Fixed if statement to so ArcGISDynamicMapServiceLayers work.
Sublayer list: clicking on a parent sublayer also sets nested checkboxes' checked property.
Merge pull request #1 from WSDOT-GIS/add-layer-list

Add layer list