Update to the debian page about packages

* Some people are apparently to stupid to exchange <code>DIST</code> with the distribution of choice, even though it's marked very clearly in bold just on the line above.
  So instead create a generic package that will generate the correct source file depending on their distribution.
  + Bump the package version number accordingly.
* Added the dailies sources lines (commented out) in the template directly.
* Added the multi-arch fix in the template directly - we only supply amd64 packages anyway so make this default.
* Add an example on how to get the GPG key and use apt-key to add it to the system keyring.