use blockHash/logIndex as the unique placement ID

[will-wow]

Goal

Use the blockHash/logIndex to uniquely identify placement events

Solution

• make blockHash/logIndex the composite primary key for placements
• use ${blockHash}_${logIndex} as the ID in geoJson files
• do an upsert to do idempotent handling of placements in /sync

Notes

• This will make you blow your db away 😞 , because we need to re-add block hashes and log ids. But you can re-sync to get all the existing stuff back