- introduce Query Context (Qcx) for managing database-per-shard.
- replaces the MultiTx, so mtx.go is retired and removed.
- introduces the HolderConfig struct and all Holders now have
a path from birth.
- rbf speedups on bitwise writes
- badgerdb is removed due to unresolvable write conflicts.
fixes#703#676
not overflow two big arrays into an invalid array.
recreate badloader from git history, at 85fa67e8. Could not
reproduce this, but lots of container usage
also got updated in the meantime.
Fixes#683