I-SEM market added

Integrated Single Electricity Market, (the combined market for IE and NIE) is added. We have named it SEM. Equivalent to how we handle, e.g. NordPool and Italy, the variables for weather, fundamentals, prices and REMTI, etc. are depicted and made available via our web and database. The symmetry in handling also means that we keep the content for IE and NIE. Historical data (Actual, Backcasts), Seasonal normals and Forecasts are, of course, provided for all variables.