relax SVN archive

Added support for the model argument for the frame_order.pdb_model user function.

This argument is used to specify which of the models in an ensemble will be used to represent the
average domain position Monte Carlo simulations, as each simulation is encoded as a model, as well
as for the distribution of structures simulating the motion of the system. The argument is
therefore passed into the create_ave_pos() and create_distribution() functions of the
specific_analyses.frame_order.geometric module.

To handle all models being used in the non Monte Carlo simulation PDB file and only one in this
file, the internal structural object is copied twice. The second copy for the MC sims has all but
the chosen model deleted out of it.

Fix for the pipe_control.error_analysis.covariance_matrix() function.

The set_errors() API method is parameter specific, so a loop over the parameters using the
get_param_names() API method has been added.

Removed the specific_analyses.relax_fit.estimate_rx_err module import.

The module has been merged into the specific API module.

Shifted the contents of the specific_analysis.relax_fit.estimate_rx_err module into the API.

The estimate_rx_err() function is now the covariance_matrix() method of the specific API. The code
for calculating the covariance matrix and errors are now in the function
pipe_control.error_analysis.covariance_matrix(), so this has been removed. And the error setting is
performed by the set_errors() API method, so that code has been deleted as well.

Missing imports in the pipe_control.error_analysis module for the covariance matrix function.

Modified pipe_control.error_analysis.covariance_matrix().

The call to the API covariance_matrix() method now has the model_info argument passed into it. For
the relaxation curve-fitting, this allows the loop over spin systems to be skipped.

Created the specific analysis base API method covariance_matrix().

This defines the arguments required and what is returned by the method. It raises the
RelaxImplementError for all analyses which do not implement this method.

Creation of the error_analysis.covariance_matrix user function.

This is simply a code rearrangement. The relax_fit user function module was duplicated and
relax_fit.rx_err_estimate renamed to error_analysis.covariance_matrix. References to the specific
analysis have been removed.

Modified the Relax_fit.test_curve_fitting_height_estimate_error system test.

The call to relax_fit.rx_err_estimate has been replaced by the yet-to-be implemented
error_analysis.covariance_matrix user function.

Implemented the pipe_control.error_analysis.covariance_matrix() function.

This follows from http://thread.gmane.org/gmane.science.nmr.relax.scm/23526/focus=7096. It will be
used by a new error_analysis.covariance_matrix user function. And it calls the specific API methods
model_loop(), covariance_matrix(), and set_error() and the relax library
lib.statistics.multifit_covar() function do to most of the work.