DMol3 calculator

This is an ASE-FileIOcalculator for the DMol3 software for energy and force calculations complete with io functions for file formats .car, .incoor and .arc.

Read functions in calculator include eigenvalues, occupation, k-points, and DMol3 .grd orbital files.

Supported periodic boundary conditions are [1,1,1] and [0,0,0]. Therefore an exception was added for the dmol fileformats in test/fio/oi.py Since DMol3 uses a cellpar like description of the cell, the undocumented .incoor file format is used for periodic calculations. Also, DMol3 can reorient the system and therefore functions to find the inverse transformation to rotate forces back to the original ASE orientation are employed throughout the calculator.