relax SVN archive

The sconstruct script can now execute the fetch_docstrings code. The path previously did not
include the current working directory and hence the module could not be imported.

Unselected residues are now properly ignored for the value.read() function as well as all the Dasha
functions.

The value.read() function contained a bug where the residue number from the file was not being read.
Instead the integer position within the file was being used as the residue number.

The model-free spectal density function 'calc_S2f_S2s_ts_djw_dS2s' does not exist. Therefore when
using the model with the parameters {S2f, S2s, ts}, the program would throw an error and stop. The
function is actually 'calc_S2f_tf_S2s_ts_djw_dS2s'. The factor 'data.s2f_s2' also had to be
calculated in 'maths_fns/jw_mf_comps.py'.