[Tracker] suggestion: get rid of open_file_with_nautilus function in t-s-t

["Tshepang Lekhonkhobe" <tshepang gmail com>]

Hi,

Shouldn't we get rid of open_file_with_nautilus functionality in t-s-t
and  therefore have xdg-utils as a required dependency. This would
help reduce t-s-t code. Besides, this code seems only reachable only
when xdg-utils isn't installed, hence the required dependency on
xdg-utils...

In this case, open_file_with_xdg_open should suffice for opening folders.

I'd rather ask before supplying a patch because I saw some
considerable amount of code in that function whose use is mysterious
to me, so am seeking advice from the t-s-t hackers...