Descriptor EdgeHistogram added

Today I received a code donation from project VizIR from Vienna, Austria, which I already integrated in Caliph & Emir. Images can now be indexed and searched using the MPEG-7 Descriptor "EdgeHistogram". Special THX goes to Horst Eidenberger, who was so kind to send me the code. See also http://vizir.ims.tuwien.ac.at/