A description of the option 'TRANSFILE' is added to 'config.rst'.
Also, the description of options 'RTRANSFORM' and 'CTRANSFORM' is
modified. They are now combined into a single option 'TRANSFORM'.
The files from the original vasp-interface repository are reshuffled in
accord with the directory structure of dft_tools. Some of the directories,
such as 'test' (unit tests for the interface), 'examples' (simple examples for
the development purposes) are temporarily placed into 'python/vasp' directory
to avoid confusion with integral tests and examples of dft_tools.
