By New York City Correspondent Sasha Smith I am about to start the most demanding — and exciting — phase of attaining the Wine & Spirit Education Trust (WSET) diploma, a hardcore wine qualification that’s held by about 100 people in the U.S. and is the stepping stone to the hardest-core wine qualification of them all, the Master of Wine. On January, 15 I start Unit 3, Light Wines of the World. (There are 6 units in all, with the others covering the wine business, viticulture, vinification, sparkling and fortified wine, and spirits.) As the extremely vague title would indicate,…