relax SVN archive

Fix for the script for calculating the numerical gradient for an exponential curve.

The off-minimum derivative was not correctly calculated.

The exponential curve numeric gradient script now uses only floating point numbers.

This is to avoid integer truncation problems.

Activated parameter scaling of the gradient in the test_dfunc_off_minimum() unit test.

This is the test class test_suite.unit_tests._target_functions.test_relax_fit.Test_relax_fit.

Fixes for the target_functions.relax_fit C module unit tests.

All values are now set to floats to avoid integer division issues.

Created a unit test to check the dfunc() function of the relax_fit C module off the minimum.

Added a script and log file for calculating the numerical gradient for an exponential curve.

This uses the data at http://thread.gmane.org/gmane.science.nmr.relax.devel/6807/focus=6840 and
calculates the gradient using the scipy.misc.derivative() function both at the minimum and at a
point away from the minimum. The values will be used to construct a unit test to check the C module
implementation.

Added several comments to the R2 eff estimate module.

task #7822(https://gna.org/task/index.php?7822): Implement user function to estimate R2eff and associated errors for exponential curve fitting.

The relax_fit C module unit tests now check if the parameter scaling is functional.

Created 2 unit tests for the target_functions.relax_fit relax C module.

These check the func() and dfunc() Python methods exposed by the module.

Big cleanup of estimate R2eff module.

This is to make the documentation more easy to read and understand.

task #7822(https://gna.org/task/index.php?7822): Implement user function to estimate R2eff and associated errors for exponential curve fitting.