add shell tool to tile entire directory of wsis

[YoniSchirris]

Fixes #50

[jonasteuwen]

Can these variables be parsed from the command line rather than have those hardcoded?

[YoniSchirris]

Yes. Added them as CL arguments.

There's much more stuff to do. I'm already using different variatoins to this script. But I guess it's ncie for people to have a template to start with.

[jonasteuwen]

Can you give an example using the GNU parallel tool? So you can run it in parallel over slides.

Perhaps we can just add this to the documentation rather than an explicit example. So I'd propose to create this in the folder examples and then we can import this in the .rst in the documentation using literalinclude. You can add the comments in the .rst itself.

[jonasteuwen]

Good enough for now.