[core] Refactor RowList.Column.defineCol as RowList.Column:

```java
import static acolyte.RowList.Column;

Column(String.class, "colName");
```
[scala] Fix inference of  on scala RowList1:

```scala
import acolyte.Implicits._
import acolyte.RowLists.stringList

stringList :+ null // fixed inference of null (as String there)
```