API: consider removing `TraversePropertiesDsl` from top-level `toDataFrame {}` operation

[Jolanrensen]

We have a very advanced Iterable<T>.toDataFrame {} API that can be quite difficult to understand. Especially because the docs need improvement: #1479

We support changing properties by name, type, or just in general:

list.toDataFrame {
  properties(A::prop1, A::prop2) {
      exclude(B::prop3)
     /* subgraph settings go here */
  }
  properties {
     preserve(SomeClass::class)
  }
  preserve(SomeOther::class)
}

now imagine my surprise when

toDataFrame { 
    preserve(DataFrame::class)
}

returned an empty dataframe, but this does not:

toDataFrame { 
    preserve(DataFrame::class)
    properties()
}

Apparently you can write multiple properties instances and top-level preserve() and exclude() calls apply to all properties {} next to them.
If I remember correctly, the compiler plugin also does not support this notation, so let's change or remove it.

Let's keep the top-level of toDataFrame dedicated to creating columns and move functions related to the TraversePropertiesDsl into properties {}. Isn't it already the case that properties(maxDepth = Int.MAX_VALUE) {} applies to every property at any depth? That already opens up a lot of possibilities. If you really want to apply the same logic to each subgraph, you could always just repeat the statement or create a variable.

toDataFrame {
    "myCol" from { it.a }
    properties(maxDepth = Int.MAX_VALUE) {
        preserve(DataFrame::class)
    }
    properties(A::prop1, A::prop2) {
        exclude(B::prop3)
    }
}