relax SVN archive

Fixes for the Hessian.py script for numerical integrating the Hessian for an exponential curve.

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 Hessian using the numdifftools.Hessian object construct and obtain the matrix, 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.

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 Newton optimisation. This is to demonstrate that the exponential curve
gradient function dfunc() and Hessian function d2func() are implemented correctly.

Implemented the specific_analyses.relax_fit.optimisation.d2func_wrapper() function.

This converts the numpy parameter array into a Python list, calls the
target_functions.relax_fit.d2func() function with this list, converts the Hessian output list of
lists into a numpy rank-2 array, and returns it. This will allow Newton optimisation to be used for
the relaxation curve-fitting analysis.

The square() function macro is now defined for the target_functions/exponential.c file.

This is defined in the header, and now the exponential.h is included in the C file to access it.

Implemented the exponential curve second partial derivative C functions.

These are declared in the exponential.h header file and are now used by the Python function
target_functions.relax_fit.d2func().

Partly implemented the front end target_functions.relax_fit.d2func() C module Python function.

This is not fully implemented as the exponential curve double partial derivatives are not
implemented.

Comment fixes and formatting changes in all of the target_functions C files and headers.

Comment fix in the target_functions/c_chi2.c file.

Clean up of the header and includes of the target_functions/c_chi2.c file.

The square() function macro has been shifted to the header file and the stdio.h and math.h standard
library headers are no longer included as they are not used.