Simplistic conversion to using renamed Chadwick module

This doesn't actually do anything, but the previous version didn't do
anything useful with the data from Chadwick.
Axe preamble hack
Rename Events to Chadwick

The class runs cwgame and cwevents, so calling it 'Events' doesn't fit.
Extensively refactor summarizing Retrosheet data

Instead of saving everything in an HDF5 file, summarize the data
immediately after reading it from cwgame/cwevent. The data still needs
to be saved. More refactoring is necessary to remove the last vestiges
of HDF5 support.