support nested JSON?

I have a nested JSON object like:
```
[
{
user : {
"fname" : "Joe",
"lname" : "Smith"
},
execution : {
...
}
}
...
]
```
I tried methods mentioned in #98 such as:
```
settings:{
columns:{
user:{
title:"First Name",
valuePrepareFunction: (user) => {
return user.fname;
}
},
user:{
title:"Last Name",
valuePrepareFunction: (user) => {
return user.lname;
}
}
}
}
```
Although this doesn't work and only displays the last one.

Is there any way to have this functionality? Or do I need to reformat my JSON?