#2 Add Output Directory Option

[Dem]

DSI currently just writes the output files (typically *.html files) into the directory containing the input files (typically *.bhtml files).

To enable users to more cleanly separate input files and output files, it would be nice to have an option to specifically set the output directory. Note that the current default behavior of using the same directory is still the desired default behavior because that is very simple and intuitive.