relax SVN archive

Split the saturation recovery exponential equations and partial derivatives into their own C file.

Implemented the target functions for the saturation recovery exponential curve.

In the Python target function class Relax_fit_opt, the new func_sat(), dfunc_sat() and d2func_sat()
methods have been created as wrappers for the new C functions. These are aliased to func(), dfunc()
and d2func() in the __init__() method.

In the target_functions/exponential.c C file, the functions exponential_sat(),
exponential_sat_dIinf(), exponential_sat_dR(), exponential_sat_dIinf2(), exponential_sat_dR_dIinf()
and exponential_sat_dR2() have been created to implement the function, gradient, and Hessian for the
equation I = Iinf * (1 - exp(-R.t)).

In the target_functions/relax_fit.c file, the functions func_sat(), dfunc_sat(), d2func_sat(),
jacobian_sat() and jacobian_chi2_sat() have been created as duplications of the *_exp() functions,
but pointing to the exponential_sat*() functions and using Iinf instead of I0.

Added support for the saturation recovery experiment to parameter disassembly function.

This is in the disassemble_param_vector() function of the specific_analyses.relax_fit.parameters
module. This function requires each experiment to be handled separately.

Modified the relax_fit.test_saturation_recovery system test to check for Iinf instead of I0.

Alphabetical ordering of the C function imports in the target_functions.relax_fit_wrapper module.

Renamed all of the relaxation curve-fitting target functions.

This includes all of the C functions which are model specific, by appending '_exp' to the current
names to now be func_exp, dfunc_exp, d2func_exp, jacobian_exp, and jacobian_chi2_exp. And all of
the Relax_fit_opt target function class *_wrapper() methods to *_exp(). The target function class
is now only aliasing the *_exp() methods when the model is set to 'exp'.

Small fix for the relax_fit.select_model user function.

The exponential model name is now being passed into the target function class.

The model as specified by the relax_fit.select_model user function is now finally being sent into
the target function, in this case the Relax_fit_opt class in target_functions.relax_fit_wrapper.

Fix for the relax_fit.select_model user function backend for the 'sat' model.

Modified the Relax_fit.test_saturation_recovery system test script.

The relax_fit.select_model user function call now selects the 'sat' model.