reworking the DB struct godoc
reworking the DB struct godoc

alberts/gorocks,jmhodges/levigo_leveldb_1.4,influxdb/levigo,influxdb/hyperleveldb-go,influxdata/hyperleveldb-go,elijahandrews/levigo,DanielMorsing/rocksdb,jmhodges/levigo,chanxuehong/goleveldb,evanphx/levigo,mikefaille/rocksdb-go,influxdb/rocksdb,dckit/rocksdb,influxdata/rocksdb