Implemented picture_load_exif_data using libexif

Earlier, exif.cpp was being used but the implementation being in c, the function
is now implemented using libexif library. This function loads latitude,
longitude and timestamp present in a picture. Absence of these should set the
values to zero.

Signed-off-by: Venkatesh Shukla <venkatesh.shukla.eee11@iitbhu.ac.in>