By Francesca Landini and Keith Weir MILAN (Reuters) -Campari sales jumped in the first three months of the year as pubs and restaurants reopened in Europe, with demand further boosted by premises stocking up on spirits before price rises take effect, the Italian drinks group said on Tuesday. Revenue came in at 535 million euros ($561 million) in the first quarter, up 29% on a like-for-like basis, more than double the increase pencilled in by analysts. Chief Executive Bob Kunze-Concewitz said that stockpiling accounted for nearly half of the increase. The maker of Aperol and Campari bitters is …