Add more logging to importgtfs
Bulk create objects 3x speedup
Cache related IDs, write in 10K batches
Export in batches, plus logging
Cache related fields on export, 12x speedup
Break up huge feed files so they can be exported
Improve logging for management commands
Refactor Base.objects.export_txt to Base.export_txt
Refactor into BaseQuerySet.populated_column_map
export_txt: Factor out write_rows
export_txt: remove feed loading
export_txt: move related names cache out of loop
export_txt: use the cache to split up huge datasets