relax SVN archive

Switched the optimisation algorithm in test_suite/system_tests/scripts/relax_fit.py.

This script, used by the Relax_fit.test_curve_fitting_height and Relax_fit.test_curve_fitting_volume
system tests, now uses the BFGS optimisation. This is to demonstrate that the exponential curve
gradient function dfunc() is implemented correctly and that more advanced optimisation algorithms
can be used (excluding those that require the full Hessian d2func() function).

Fix for the test_dfunc_off_minimum() unit test.

This is the test class test_suite.unit_tests._target_functions.test_relax_fit.Test_relax_fit. The
wrong gradient was being scaled.

Bug fix for the chi-squared gradient calculation in the C module.

The definition of the square() function needed extra brackets so that the 1/error**2 calculation
would be 1/(error*error) rather than the incorrect 1/error*error form.

Increased the printouts for the script for calculating the numerical gradient for an exponential curve.

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.