LevelDB IO issue

[SmartArray]

Waiting for RPC node to be ready...
/home/digibyte/rosetta/digibyte-rosetta-server/node_modules/levelup/lib/levelup.js:119
      return callback(new OpenError(err))
                      ^
OpenError: IO error: /home/digibyte/rosetta/digibyte-rosetta-server/data2/metadata/LOCK: No such file or directory

This error happens although the mentioned file exists.

Potential fix: Use only one instance of leveldb file.

[SmartArray]

Only one LevelDB instance will be used now: 6359615

Keys are all encoded with prefix bytes:

const PREFIX_BLOCK_SYM     = 'B';
const PREFIX_TX_SYM        = 'T';
const PREFIX_UTXO          = 'U';
const PREFIX_ADDRESS_UTXOS = 'X';

to have different namespaces within the data.
All keys are encoded as binary data, or at least strings.

[SmartArray]

Removed ADDRESS_SYM namespace: 1149fc8

[SmartArray]

First test sync to block 5000 worked quite well.
However, restarting the node doesn't sync from the previous checkpoint.

[SmartArray]

Fixed with: e51820e