Support for large structures

[aebrer]

From OSL:

http://www.wwpdb.org/news/news_2014.html#10-December-2014
Large structures have come to the PDB. This may explain the unusually high number of not-found files during the update currently in progress. The principal investigators will need to help us understand how this change impacts the PGD and what sort of code changes if any will be required.