Added holidays and vacation effect in MW

EQ simulates the expected effect on power consumption due holidays, bridging and vacations. The time series, available for download, comprises many effects: 1. Shoulder effects: Ramping down the day before a holiday and ramping up as workload resumes the following day. 2. Bridging: The impact of businesses (employees that take a day off the day after or before a holiday). 3. Overlapping holidays: Adjusting for holidays that coincide. 4. Vacation effect: Predominately the summer vacation, measured as reduced load.