Check wrap option on a despray generates multiple file parts

From my current reading of the code (untested) it looks like if you despray a file with the wrap=1 option it will not generate a destination filename that contains $P$_of$N$

(It may need to call constructFileMask() if that option is set).

I may be misinterpreting what the wrap option is meant to do - in which case we will need to add a new option which keeps the individual parts.