By Hadeel Al Sayegh, John O’Donnell and Elizabeth Howcroft LONDON/DUBAI (Reuters) – Palestinian militant group Hamas uses a global financing network to funnel support from charities and friendly nations, passing cash through Gaza tunnels or using cryptocurrencies to bypass international sanctions, according to experts and officials. However, Hamas, which governs the Gaza Strip, will face even more obstacles accessing funds after the rampage by the group’s gunmen that killed hundreds of Israelis, mainly civilians. Israel has responded with the heaviest bombardment of Gaza in 75 years of conflic…