Add Privilege doxygen tag to get storage image size
Add Privilege doxygen tag to get storage image size

- ResourceImage::GetImageSize() needs privileges to media storage and external storage

Change-Id: I9179a2e651611875129f9c6d7ae50f8ba7da6efa
Signed-off-by: Seoyeon Kim <9d7945f986357c1681706fda3daa4250c146b2e7@samsung.com>

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