relax SVN archive

Modified the ScientificPython structural object atom_loop() method to match the internal object.

If only one element is returned from the atom_loop(), then this is returned as a single item rather
than a tuple of length 1.

Implemented the Internal._trim_sheet() internal structural object method.

This is also now used by the structure.delete user function to remove sheet metadata for residues
which no longer exist.

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

These are mirror the 13 unit tests of Internal._trim_helix().

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.