By Nidal al-Mughrabi and James Mackenzie GAZA/JERUSALEM (Reuters) – Israel reopened border crossings into Gaza on Monday following an Egyptian-brokered ceasefire with the militant Islamic Jihad group that ended the most serious outbreak of fighting around the volatile Palestinian enclave in more than a year. At least 44 people, including 15 children, were killed in 56 hours of violence that began when Israeli airstrikes hit a senior Islamic Jihad commander. Israel said its action was a pre-emptive strike against an attack planned by the Iranian-backed group. Hundreds more people were wounded a…