The following data types for attributes are implemented:
 - int
 - double
 - cv::String
 - cv::InputArray

 - Some test cases are added
 - Two tutorials are written to show how to use it.

Close unused resource in dscreate and dsread. Otherwise, the file will not be close when close() is called.

See  the following for Delayed close, which is close dataset after exe terminate: https://www.hdfgroup.org/HDF5/doc/RM/RM_H5F.html#File-Close

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