The commander of the Philippine Navy was abruptly sacked Tuesday in a surprise move which a legislator and news reports linked to a dispute about a contract for warships.Vice Admiral Ronald Joseph Mercado was replaced by Rear Admiral Robert Empedrad in compliance with "the instructions from higher authorities", said military spokesman Colonel Edgard Arevalo."The reason for this change of command will be explained in due time," Arevalo said in a statement.The navy spokesman