[BUG] Restored ability to detect FHIaims geometry file by file extension

Closed username-removed-268789 requested to merge schober-ch/ase:bugfix/aims_files into master

Small change to formats.py restores the ability to detect FHIaims geometry.in file by the file extension (.in), as it was in the old io code.

Edit: Sorry for the whitespace things, I realized that my vi automatically removes things like spaces/indention in blank lines. If the indention in the ase files is intentional, I can change this in my merge request.