Modify standardization & use of crash data to permit crashes by month rather than week

[terryf82]

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[terryf82]

Certain cities (Philadelphia and Brisbane at least) provide crash data with no day of month property, for privacy reasons.

For these cities to work we need to look at upgrading at least two processes:

1. the standardize_crashes script needs to understand when the raw crash data has no day of month property and record the available date accordingly
2. the modeling process needs to know the city uses per-month crash data (by reading the config?) and generate predictions of the same nature.

[terryf82]

PR 181 implements something of a work-around for this issue, so that we can continue onboarding cities that choose not to supply the date of month for crashes (Pittsburgh, Brisbane and Philladelphia so far).

The initialize_city script now provides additional options for specifying different date formats, with date_complete, or in combination date_year, date_month and date_day. This last one is optional, because some cities like those mentioned above withhold the day of month to anonymize the crash data. If this field is left blank, standardize_crashes will pick a random day of the month and assign it.

I don't know there's any point in moving further on this, until we decide the value of temporal predictions (by week, month or any other period) versus simply predictions at point of execution.