Row Expression / DataRow improvements

[Jolanrensen]

There are a lot of parallels between the Column(s) Selection DSL and Row(Value)Expressions as both allow you to reference columns. The difference being that referencing a column on a DataRow produces a value as in the Column(s) Selection DSL it produces a column.

Still, it's worth revisiting DataRow.kt keeping in mind the parallels with the improved Columns Selection DSL (after that's done).

One thing that comes to mind is being able to call "column"() without a type to reference an Any? column and the "easy"["creation"]["of"]["columnPaths"].get<T>("withSingleColumnAccess").