Option to replace command same name (#374)

* option to replace command same name

* moved order of custom value declarations

* arranged dataframe folders and objects

* sort help commands by name

* added dtypes function for debugging

* corrected name for dataframe commands

* command names using function

crates/nu-command/src/formats/to/json.rs

@@ -73,7 +73,6 @@ pub fn value_to_json_value(v: &Value) -> Result<nu_json::Value, ShellError> {
             }
             nu_json::Value::Object(m)
         }
-        #[cfg(feature = "custom")]
         Value::CustomValue { val, .. } => val.to_json(),
     })
 }