By Andrew Mills DOHA, July 12 (Reuters) - Qatar's former emir, Sheikh Hamad bin Khalifa Al-Thani, a sweeping moderniser who seized power in 1995 and broke with tradition to hand it over to his son 18 years later, has died at the age of 74. Qatar's top government body, the Amiri Diwan, announced that Sheikh Hamad had died on Sunday morning. It did not mention the cause of his death. The Qatar that the current Emir Sheikh Tamim bin Hamad Al-Thani inherited was already well on its way to being…