Reopen the files in the software as well

[TeoColuccio]

The extension would really be the best if it could also reopen the files you were working on at the time of saving. For example, if I am working on pdfs opened with evince and odts opened with writer, at the time of the resume, evince and writer will only be reopened but not the files I was working on.

[nashamri]

I'm so interested in this, but it might be not easy to implement. I've tried to add extra arguments manually to the cmd entry in the session file, but it didn't work. It only works when I remove the the desktop_file_id and "desktop_file_id_full_path entries, but then I lose the ability to restore the windows sizes and positions.

[nlpsuge]

It only works when I remove the the desktop_file_id and "desktop_file_id_full_path entries, but then I lose the ability to restore the windows sizes and positions.

After I finish this PR #67, the windows sizes and positions will also be restored when desktop_file_id is absent.