REFAC: history for mixed sampling data handler
currently this data handler uses hourly data from t-x to t0 (1H) and targets t+1 to t+x (1d). But in terms of input data t+24 (1H) = t+1 (1d) and therefore there are 23 hourly values missing. Correct this to use the entire day of t0 instead of the single value at 00 hour.