Cannot pass multiple inputs to a model

[jatkinson1000]

At present the library only allows us to pass a single tensor to a model and receive a single output tensor.

This needs updating so that we can pass multiple input tensors.

In the Fortran:

• Instead of passing an input tensor pass an array of tensors.
• Get the length of the input array of tensors and pass that to the c++

In the c++:

• loop over the number of tensors and append (.push_back) on to the inputs to the C function.