A few days ago, I was given a lovely gift. A big jar of preserved lemons.   I know Moroccan preserved lemons, but had never met Chinese ones. In fact, apart from in the south, in many parts of China it isn't that easy to find lemons, at all.   These are apparently a speciality of the southern Zhuang minority of Wuming County near Nanning. The Zhuang people are the largest ethnic minority in China and most live in Guangxi. These preserved lemons feature in their diet and are u