Change IFrame interface to be able to pass DataType

[jafet-chaves]

There is currently a limitation with the IFrame interface in the sense that it doesn't allow to pass a DataType. Basically no matter the type of pointer that one passes with Configure methods, all backends are returning r2i::DataType::Id::FLOAT in their GetDataType implementations.

This limits possible checks that can be done in the postprocessing modules for example.