bugfix: move site-cookbooks to cookbooks

i have had problems with stuff in site-cookbooks, as the default pulls in everything from cookbooks and berkshelfs internal store

Signed-off-by: Dominik Richter <dominik.richter@gmail.com>
update berksfile to current syntax for source

Signed-off-by: Dominik Richter <dominik.richter@gmail.com>