False positive errors on field names starting with underscores 

The following queries have valid syntax but are highlighted as invalid:

```cypher
MATCH (f:Foo)
WHERE f._type = $type
//      ^ <function name> or <symbolic name string> expected, got '_'
```

```cypher
MATCH (f:Foo)
WHERE f.type = $data._type
//                   ^ <function name> or <symbolic name string> expected, got '_'
```