relax SVN archive

Reordered the debugging command line options and removed the '-r' shortcut.

Created the '--error-state' command line option for saving a pickled state when a RelaxError is raised.

This gives greater control of a powerful feature added to relax by Chris MacRaild. The pickled
state can then be attached to bug reports or can be used to quickly load the state prior to failure
when in the scripting UI mode.

Clean up of the debugging command line options.

The debug flag now will cause stack tracebacks to be printed on all RelaxWarnings.

Created the new '-r' or '--traceback' relax command line option.

When supplied, then stack tracebacks will be shown for all RelaxWarnings and RelaxErrors. This
allows for finer debugging control.

Created the lib.warnings.TRACEBACK variable.

When True, this will cause stack-traceback to be printed out with the warning. This is to decouple
the traceback printout from the warning to error escalation.

Converted the status.escalate variable into module variables for lib.errors and lib.warnings.

This variable is set by the command line flag '-e' or '--escalate'. By converting it into a module
variable, the lib.errors and lib.warnings warnings are now independent of relax.

Implemented linear constraints for the frame order analysis.

This uses the log-barrier constraint algorithm in the minfx library https://gna.org/projects/minfx/
to provide constraints without requiring gradients.

Docstring fix in the relaxation curve-fitting linear_constraints() function.

The pivot point x, y and z coordinates are now registered as parameters of the frame order analysis.

These are stored as the parameters pivot_x, pivot_y and pivot_z.

Docstring update for the relaxation dispersion linear_constraints() function.