Generalise Eigen inputs for adj_jac_apply

## Description
```adj_jac_apply``` currently only works for ```Eigen::Matrix<T, R, C>```, by generalising it to work with any Eigen inputs, the framework can then be used with ```Eigen::Array``` types or other Eigen expressions (e.g. ```softmax(m.diagonal())```).


#### Current Version:
v3.1.0
