* Ex-rebels alleged to have taken organs from Serbs
* Kosovo government, led by ex-guerrilla, rejects charges
* Concerns over witness intimidation in Kosovo
By Fatos Bytyci
PRISTINA, April 4 (Reuters) - Plans are under way for a European Union-backed special tribunal to try Kosovo Albanian former guerrillas accused of harvesting organs from murdered Serbs during the Balkan country's ...