Parse reference entries, i.e. _See_ other word

e.g.

```
 "4345": {
  "variants": ["vithall", "-in"],
  "partOfSpeech": null,
  "entry": "#Vithall#, #-in#, _See_ Withal, -inne."
 },

// in the lookup
 "vithall": ["4345", "4636"],
 "-in": ["4345"],
```