Addition of FHI-aims interface to CASM

[janklinux]

Still needs functional testing which I am on right now, for now:

1. The user HAS TO define the DFT code in the relax.json of other than vasp
2. casm setup works for FHI-aims
3. There has been some redefinition and reorganization of internals read / write of the settings i.e.
4. Some streamlining of code could be done with respect to common routines and code-specific interfaces
5. For FHI-aims there is new functionality in terms of surface definitions and relaxation settings that can fix specific parts of the slab
6. I cleaned up the code to PEP8 in the files I made changes to
7. I strongly recommend using at least PEP8 standards to maintain python code readability