Better commandline option parsing

[simonzack]

This PR improves commandline option parsing by matching more option types, so commands like the following (created by yaourt) works:

sudo pacmatic --color auto -U /tmp/yaourt-tmp-linux/PKGDEST.tVK/test-x86_64.pkg.tar.xz

I've also changed the conditions where pacdiff is called, to include the pacman -U option, and to exclude cases where no new packages are installed, which I hope is reasonable.

explode_args comes from yaourt (GPL).