relax SVN archive

Import fixes for the lib.structure.internal.displacements module.

Moved the residual pipe_control.structure.api_base module to lib.structure.internal.displacements.

This is because the base module still contained the Displacements class.

Updated the package __all__ list for some unit tests.

Deleted the unit tests of the structural API base class.

Merged the structural API base module api_base into pipe_control.structure.internal.

The API base class is no longer needed as the ScientificPython PDB reader has been eliminated.

Fixes for more missing imports into lib.structure.internal.molecules.

Missing import.

Import fixes for the structural object module rearrangements.

Total elimination of the ScientificPython PDB object.

Maintaining this reader was too much effort and the internal structural object has now surpassed
the capabilities of the ScientificPython PDB object (for example the internal object is not PDB
specific). And ScientificPython is very much a dead project, largely replaced by the more
successful scipy.

Import fix form the previous commit.