Refactoring: more granular AbstractStructureParser model (resolves request #15)
Refactoring: more granular AbstractStructureParser model (resolves request #15)

csb.bio.io.wwpdb:
  - AbstractStructureParser._parse_atoms will now delegate to a number of hook methods, which clients can override
  - improved error handling of malformed ATOM records
  - improved  error handling of malformed headers
  - extended documentation

csb-toolbox/CSB