6CYANA: write spectrum - CYANA command

Parameters: file=<filename>                (required)
            format=bruker|ucsf             (default: ucsf)
            specnum=<integer>              (default: 1)

Writes a binary spectrum file in Bruker or UCSF format. If
a Bruker file is written processing parameter files are
written as well. If more than one spectrum have been read
the spectrum to be written is selected by 'specnum', which
refers to the order in which the spectra were read.

Note: Bruker files may need to be placed in a certain directory
structure for other software to be able to work with them. In
such a case the path of the data directory needs to be of the
form <working directory>/<sub directory>/pdata/<integer> .
