Converts the specified list of columns to the specified type.  The types
are specified by the following strings:

- "boolean"
- "byte"
- "short"
- "integer"
- "long"
- "float"
- "double"
- "string"
- "toCategorical" - make the column be a categorical column
- "clearCategorical" - clear the categorical column
- "date" - the default date format is: "yyyy-MM-dd HH:mm:ss"
