improve packaging, update to latest version from Launchpad

I've copied the files from the PPA source package and improved some packaging related issues (errors and warnings when checking the package with `lintian steam-login*.deb`):

 * upload changelog and fix syntax errors
 * recommend `steam | steam-launcher` in debian/control
 * install script into `/usr/games` since the package is categorized as `Section: games`
 * build binary package from actual source package using `dpkg-buildpackage` command
 * install pdfs as docs and not into `/usr/bin` (what is this actually? does this need to be in the package? looks a bit like spam to me)