Improvements / Additions to the base chef-repo

Hello,

This is my first pull request so I apologize in advance if I'm not doing something correctly.

First, I modified the 'chefignore' file to ignore more files by default (it's basically the same as the 'chefignore' automatically generated from 'https://preview.opscode.com/organizations'; however, I think the original 'chefignore' handled svn better so I kept that configuration)

Next, I added sample .chef/knife.rb and .chef/SAMPLE.knife.rb files with lots of comments; hopefully these will make it easier for users to get started in a shared environment.

Finally, I added the new knife.local.rb to the gitignore file (since it's unlikely that users will want to commit this in a shared environment).

Hopefully this is helpful :-)

Thanks,
Nick Henry