[Dcmlib] Private GE 'Implicit VR' Big Endian Transfer Syntax 16 Bits image

[Jean-Pierre Roux]

The reported trouble on Private GE 'Implicit VR' Big Endian Transfer 
Syntax 16 Bits images is fixed.
A sample image is added in gdcmSampleData/images_of_interest, as 
PrivateGEImplicitVRBigEndianTransferSyntax16Bits.dcm + 
PrivateGEImplicitVRBigEndianTransferSyntax16Bits.README.txt

Thx to Illona Mulleder and Florian Pierron for providing data to fix the 
bug.

JPRx