More info when trip_purpose_and_destination has high fail rate

[bstabler]

When first setting up the iterative trip_purpose_and_destination model, some users get high trip fail rates, which is likely due to inconsistencies upstream related to input data, expressions, etc.. To aid in debugging, it would be good to produce more information that helps users understand the issue. For example, maybe we can produce a crosstab of trip fail rate by purpose and mode.