JsonSource should support path expressions

# JsonSource should support path expressions

# Scenario

- If I have defined a structure like the following:
```sql
struct Person {
name:String,
age: Int,
sex: String
}
```
- I should be able to specify a projection like so:
```scala
withProjection("person.name", "person.age")
```

- The above returns scalar values for name and age.
- Likewise I think it should work for **withPredicate**
- Jackson has has processor for drilling into nested types using path expressions which are similar to XPath
- You could put forward a case that this syntax should be the language for other formats that support nested types, Avro, Parquet and Orc