identify best PDB/molecule file formats

[luponzo86]

We need to identify a more flexible file format that handles large structures better than PDB.
Possible candidates:

• PDBx/mmCIF which is the update and official format of RCSB PDB, see http://www.wwpdb.org/documentation/file-formats-and-the-pdb
• .mol v3000, although it seems to be not back compatible...