relax SVN archive

Fixes for the helix metadata deletion for the internal structural object.

This affects the structure.delete user function.

Fix for the internal structural object _trim_helix() method for the helix metadata format.

Modified all of the unit tests of the internal structural object _trim_helix() method.

The structure of the helix metadata in the internal structural object was not correctly mimicked.

Implemented the internal structural object _trim_helix() method.

This is used when the structure.delete user function is called to trim and remove the helix
metadata. For this to work, the additional method _residue_data() was written to create a
dictionary with residue numbers as keys and the residue names as numbers. This dictionary is used
by _trim_helix() to change the residue names in the helix metadata.

Fixes for some of the new unit tests of the internal structural object _trim_helix() method.

Fix for the unit test of the generic_fns.structure.pdb_write.helix() function.

The init_seq_id argument is now called init_seq_num to match the PDB notation.

Fixes for some unit tests of the internal structural object for the changes to the atom_loop().

Single elements are now returned as single elements rather than a tuple of length 1.

Docstring editing of the ScientificPython structural object atom_loop() method.

Added the index_flag argument to all structural API atom_loop() methods.

Created 13 unit tests of the Internal._trim_helix() internal structural object method.