Blurb:: Export sample sequences enabling file format customization 

Description:: 

Sample sequences are written on file with a user-defined format. If the keyword \c header is
present the heading is used, if the keyword \c eval_id is present the sample number (per level)
is included and if \c interface_id is provided then the interface identification is reported. 

Examples::

The following method block 
\verbatim
method,
	model_pointer = 'HIERARCH'
        multilevel_sampling
	  pilot_samples = 20 seed = 1237
	  convergence_tolerance = .01
	  output silent
	  export_sample_sequence custom_annotated eval_id
\endverbatim

results in enabling the sample output on file with a customized format including only
the progressive number of the sample (\c eval_id).



