Invalidate last calculated indicators when new GTFS uploaded
Fix ErrorFactory initialization in celery shapefile upload.

Fixes #138.
Delete shapefiles for other cities on GTFS upload
Only invalidate indicators for city on upload
Move `city_name` from `Indicator` to `IndicatorJob`
Merge pull request #176 from flibbertigibbet/feature/delete-by-city

Feature/delete by city