relax SVN archive

Shifted part of the internal structural object into the lib.structure.internal.models module.

This contains the two classes ModelList and ModelContainer from the pipe_control.structure.api_base
module.

Created the empty lib.structure.internal package for holding the internal structural object.

More decoupling of the internal structural object from the relax data store.

Removed the ability of the internal structural object to determine if two atoms are connected by
consulting the relax data store.

Removed the data pipe checks from the internal structural object.

This decoupling from the relax data store is in preparation for moving into the lib.structure
package.

Package __all__ list updates.

Import fixes for the recent rearrangements.

Split the pipe_control.structure.mass module into two with the CoM code going to lib.structure.mass.

Shifted the pipe_control.structure.cones module to lib.structure.cones.

Shifted the pipe_control.structure.pdb_read and pipe_control.structure.pdb_write modules to lib.structure.

Created the unit test infrastructure for the lib.structure package.