make deb packages use correct architecture and increasing version

this will make our auto-generated deb packages use the correct architecture (previous to this PR, it is set to i386 at all times), automatically generate dependencies, and append the date of the last git commit to the version string (this is a common practice that ensures an increasing version string). I have also removed the Debian suffix from the version number as this is only applicable for packages with distribution-level patches.
As make package is not (currently) suitable to automatically generate official Debian/Ubuntu packages (it can't create self-building source packages), this should not affect official packaging efforts.
It should not fail when git/dpkg are not available (I've renamed them on my ubuntu system and build completes as normal) but if anyone has a non-debian system around a test may be worthwhile. (would Travis work for this? we'll see I guess)