Initialises a storage variable for sopi.
sopi_begin() sopi_begin(verbosity)
the verbosity level of sopi (default is 0)
This routine creates a global variable sopiData in which some internal elements required for sopi to work are stored. This routine must be called prior to any sopi-related operation or they will not work. If this variable is altered, unexpected things will happen.
In addition, it also enables to set global properties for sopi.