Implement Automatic Differentiation library using Cling

by Martin Vasilev for CERN SFT

Automatic differentiation is the process of obtaining a derivative of specific function in terms of computer transformations. This proposal provides a plan for improving and implementing missing features of the clang based automatic differentiation plugin clad. The plan is divided into steps. Each step is separated as an individual task where a short description of the problem is presented. The goal of the project is to implement functionality that is able to differentiate non-trivial functions.