relax SVN archive

The printouts from the structure.read_pdb user function are now different with the merge flag set.

The text now says that the molecules are being merged rather than added.

Bug fix for the structural data consistency test in the pack_structs() structural API method.

The index was not correct causing failures in certain rare cases.

Fixes for the test suite for the changes to the Ap4Aase PDB file atom numbering at r18855.

Implemented the merging of structural objects.

This allows the merge flag of the structure.read_pdb user function to work.

Fixes for all the Ap4Aase truncated PDB files.

The atom numbers are now sequential, as defined by the PDB standard.

Fix for a copy and paste error in the Structure.test_read_merge system test.

Replaced many instances of the tab character '\t' with 4 spaces.

The MolList.add_item() structural API method now returns the added molecule container.

This is used by the pack_structs() method to alias the molecule, and will be required when structure
merging is implemented.

The merge flag for the structure.read_pdb user function is now propaged to the pack_structs() method.

This structure API method calls the ModelList.merge_item() method which is yet to be implemented.

Docstring fix for the structure.read_pdb user function backend.