- Don't covert grey level pixels+LUT to RGB pixels before compression

- Don't covert grey level pixels+LUT to RGB pixels before compression
- Check pixels on the right legth (for odd length data)
- Allow a difference of +/-1 between native image and decompressed image for
each pixel
- Display the warnings at the right place
- Count successes and failures

Warning :

-> It seems that *all* the failures 'pixels differ as expanded in memory'
   shouldn't appear (resulting image looks perfect ?!?)

-> For some images :
gdcmData/05115014-mr-siemens-avanto-syngo-with-palette-icone.dcm
gdcmData/05119865-mr-siemens-avanto-syngo.dcm
gdcmData/05148044-mr-siemens-avanto-syngo.dcm
gdcmData/CT-SIEMENS-Icone-With-PaletteColor.dcm
gdcmData/GE_CT_With_Private_compressed-icon.dcm
gdcmData/MR_GE_with_Private_Compressed_Icon_0009_1110.dcm
gdcmData/SiemensMagnetomPhoenixWithCSAinfo.dcm
gdcmData/MR-sonata-3D-as-Tile.dcm
gdcmData/CT_Phillips_UNvsSQ_fixed.dcm
gdcmData/MR-SIEMENS-DICOM-WithOverlays.dcm
gdcmData/MR-SIEMENS-DICOM-WithOverlays-extracted-overlays.dcm
gdcmData/PICKER-16-MONO2-Nested_icon.dcm
gdcmData/PrivateGEImplicitVRBigEndianTransferSyntax16Bits.dcm

compression leads to non gdcm-parsable result.
:-(