enable images

[mfrasca]

I made some attempts with including png files and it seems quite simple...
but I need remove some hard coded stuff.

[mfrasca]

when doing rst files, you might either hope that we collect the needed images according to the rst text, or explicitly.

[mfrasca]

to include the images, we could use something like this:
--images *.png

they would not be included as if they had to go on separate pages, but just so that the rst files can find them in the /content subdir (that is, the same as the text files themselves).