Explicit incarnation map in the database for deleted contracts (#578)

common/dbutils/bucket.go

core/genesis.go

core/state/database.go

core/state/db_state_reader.go

core/state/db_state_writer.go

core/state/plain_state_reader.go

core/state/plain_state_writer.go

core/state/readonly.go

core/vm/gas_table_test.go

eth/downloader/stagedsync_stage_execute.go

eth/downloader/stagedsync_stage_execute_test.go

ethdb/walk.go