Add adaptive integration method as a extension to expanded ensemble - Redmine #1849

We implemented the adaptive integration method (DOI: http://dx.doi.org/10.1103/PhysRevE.69.056704) by extending the expanded ensemble functionality in GROMACS 5.1.4. The published paper is here: https://peerj.com/articles/cs-264/. I would like to add this method as a feature to the next major release of GROMACS. I understand there have been major changes to the structure of the working code and a Python wrapper has also been implemented (very exciting by the way). I also recall there were talks of changing the expanded ensemble code in the developer mailing list. As I haven't been involved in the code changes I will have to review the current version but I don't expect any major complications.