Hierarchical dynamic containers for fusion data

The core library is written in C++11, highly leveraging the Boost library, and provides bindings for C, FORTRAN and Python (other languages are foreseen). The intent is to provide a clean, simple and universal API, that can be also used for unified access of files or databases. HDC is planned to be used in IMAS and for COMPASS, JET, MAST-U and TCV databases.