added some fields to session data

data.nBaselineHours - number of baseline hours before adding the active substance (baclofen, CNQX)
data.unitFullHours - number of hours each unit showed activity
data.networkFullHours - number of hours all units showed activity (except for discarded short units)
data.maxUnitFullHours - maximal number of activity hours across all units
data.nDiscardedShortUnits - number of units discarded because they had less than 7 hours of activity (including baseline)