Data Types: Introduce this concept in Integrator and Web Variables

As a model builder, I want explicitly define data types for variables to ensure accuracy and correct operation in my model.

In Admin Setting keys, it is possible to define data types :

For consistency, these data types should also be extended to Spreadsheet Server Variables

..and Integrator variables

The default type should always be string. The specification of a data type should be optional.

Right now, Spreadsheet variables and Integrator variables coerce whatever value is entered into an implicit type, depending on context. If data types could be specified, it would simplify this coercion and guarantee accuracy and correct operation.