modify default datatype for `new image` as uint8 insteaed of int64. There is a problem for compatibility with fslview.
modify default datatype for `new image` as uint8 insteaed of int64. There is a problem for compatibility with fslview.

sunshineDrizzle/FreeROI,BNUCNL/FreeROI,sunshineDrizzle/FreeROI,BNUCNL/FreeROI