introduce LAYER_UI to replace LAYER_2D, deprecate latter
introduce LAYER_UI to replace LAYER_2D, deprecate latter

Change-Id: I6228bf0e8f3153918fdac8759b0d45e8c41027e2

pwisbey/dali-core,pwisbey/dali-core,dalihub/dali-core,dalihub/dali-core,pwisbey/dali-core,dalihub/dali-core,pwisbey/dali-core,dalihub/dali-core