Always populate rating cache for every location

[joshi1983]

AccessLocator looks useless to people who have disabilities and want to learn what places will accommodate their needs. This is because only a few places have ratings in them.

Ideally, every location is rated and up to date but that's not realistic. The location search feature shows ratings where unanswered or unrated information is essentially treated as "no". AccessLocator can get smarter than that by making use of ratings on similar locations.

A few assumptions can help this gap-filling technique be more accurate:

• Locations in the same location group tend to have similar accessibility features. For example, if one Tim Hortons is at ground level and doesn't need an elevator, other Tim Hortons locations will do the same.
• Locations with similar names tend to have similar accessibility features. Similar names can mean they're in the same franchise but we simply haven't included that franchise as a "location group" yet.
• Locations in similar categories such as Restaurant, Park... tend to have similar accessibility features.

Improvements can be made later but roughly using the above assumptions to find ratings for unanswered/unrated locations should help us get reasonably accurate ratings.

This work breaks into the following subtasks:

• [x] Schema changes - add a ratings_cache field to the location_group table. Also, add an is_automatic_group field to the location_group. These new fields will be useful in storing ratings for multiple locations and making those values quick to retrieve to fill in ratings for locations within those groups.
• [ ] Create an API that populates the ratings cache for the single automatic group(the special group for locations that don't fit in any other location group).
• [ ] Create an API that populates the ratings cache for a specified location group.
• [x] Create a Python script that refreshes all location group cache.
• [ ] Adjust the location rating cache calculation to make use of the associated group's rating cache when the location has a missing rating. The missing rating could be any individual question.

[stephanosm]

This is a good assumption and we should do it. This can actually quickly add ratings through out the country and perhaps US.

[joshi1983]

This still needs some work. The ratings_cache field is in the location_group table now but I forget how much of it is working. I think a lingering question was, "when should we recalculate the group's ratings_cache values?". Maybe it should be done daily using a scheduled cron job.