Enable debian packaging with https://packager.io

This pull request adds support for packaging OpenProject for Debian 7 using Packager.io, and automatically setting up OpenProject with a wizard. It is not really meant to be merged as is, but to track the progress of the packaging process on the dev branch, and allow people to make comments.

I will extract a few separate pull requests from this branch as soon as I get back from vacation, to make the review and merging process easier.
This might be a bit picky: To properly clean up even if a command between creating and removing the temporary file fails, we should use [trap](http://www.linuxjournal.com/content/use-bash-trap-statement-cleanup-temporary-files).

Alternatively, [process substitution](http://www.tldp.org/LDP/abs/html/process-sub.html) could make this work without a temporary file:

```bash
config=$(ruby -r ...)
mysqldump --defaults-file=<(echo $config) ...
```