relax SVN archive

Fixes for the load_pdb() method.

Previously loaded structures were not being taken into account.

Fixes for the test_read_pdb_mol_2_model_scientific() system test.

The Scientific python PDB reader somehow decided to split the single structures in
'lactose_MCMM4_S1_*.pdb' into 2.

Bug fix for the load_pdb() method.

When set_model_num is None, this is now handled properly.

Duplicated 5 systems tests of the internal PDB reader for the Scientific python PDB reader.

A small fix to the system test.

However, is this fix the solution or is there something wrong with the reading of data (such as
'R2eff') by relax_data.read() ?

Shouldn't the data, for example 'R2eff', be available in 'cdp.mol[0].res[0].spin[0].R2eff_val[0]'
or 'cdp.mol[0].res[0].spin[0].R2eff[0]' for the 1st spin of the 1st residue in the 1st molecule ?

Wrote 2 new system tests for the new structural data design.

In test_read_pdb_internal6(), 2 different structures are loaded as 2 molecules. In
test_read_pdb_internal7(), 2 identical structures are loaded as 2 molecules.

Added a missing import.

Added more to the docstring.

This is not complete yet...

Reordered a few functions for alphabetical reasons.

Removed the obsolete function 'relax_disp.r2eff_read()'.

R2eff values will be read directly by 'relax_data.read()' (see r8702 and r8703).