Implement changes to setup chef-server environment 

The default recipe will setup environment for chef-server.
So user can run $ chef-server-setup command to install and configure chef-server.
Instead of package_file, could we have the following attributes?

1. package_name -- the name of the package in our apt repo. This should be set to a default value.
2. package_value -- the version number of Chef -- internally we'd use this to generate a versioned package name -- should be blank by default so we always get the latest
3. package_url -- blank by default, let's you specify a path to a .deb (or eventually a .rpm, etc.) and overrides the previous options (should fail if you set this and the others are not set to nil). Useful for testing prerelease builds that aren't available on our apt (and eventually yum) repo.