Add support of directory copy

When copying directories, files and sub-directories should be
recursively copied. And we have to update the database by scanning
the entire directory.

Test: Copy directories with sub-directories and files inside to
another location. All directories and files are successfully
copied.

Change-Id: Iea9603b51bd0a944c87dedd962804d18d11984c4
Signed-off-by: kyle_tso <kyle_tso@htc.com>