Fix column widths in output file

[YHordijk]

In some cases column headers in the pyfrag output are concatenated, for example when reading more than 10 orbital energies the column headers will be concatenated.

E.g.: ...orbital_energy10orbital_energy11...

[SiebeLeDe]

Headers are cutted in a wrong name
Sorting goes wrong due to the second index.
Frag1energy, frag2energy instead of strain