relax SVN archive

Bug fix for generic_fns.selection.exists_mol_res_spin_data(). No data pipes are now handled.

Wrote 4 unit tests for the generic_fns.selection.exists_mol_res_spin_data() function.

Wrote the exists_mol_res_spin_data() function.

This function determines if any molecule-residue-spin data exists.

Added a unit test, the counting of the number of spins should raise an error when no pipe exists.

Fix for the test_count_no_spins unit test - a data pipe now exists.

Added a unit test for the proper operation of the molecule loop when no data pipe is present.

Added a unit test for the proper operation of the spin loop when no data pipe is present.

Fixes for the unit tests of the spin and molecule loops when no data is present.

Fixed the unit test of the residue loop with no data pipes present.

The unittest framework couldn't handle the generator function, so an intermediary function was
created!

Added a unit test for the proper operation of the residue loop when no data pipe is present.