Combine events and powers into single data structure

[zduey]

We assume that the rows of the 2D feature matrix matches the order of events stored in a recarray. This requires us to be very careful any time events or powers are modified in a way that could scramble this ordering. It would be better if these two structures were combined so there was less room for error in processing these two data structures. Most likely a pandas dataframe would be the best bet.