Updates to structure project, conversion to slf4j and minor bug fixes

Conversion of org.biojava.bio.structure package (main) in biojava3-structure project to slf4j.  Minor bug fixes including printing array contents instead of address, handling potential null pointer exception
Understood, and agree. Would printing to std out be the best thing to do? It seems a bit awkward... Could a flatfile or another mechanism be more appropriate? With a log detailing such. This decision would apply to a number of locations throughout the project in addition to this one. All that being said, perhaps stdout is the most convenient for the end user. Thoughts...?