Add attributes for database spec

This commit adds two global attributes hashes for database passwords.
These are required for both mysql and postgresql server recipes.
Add service definitions for gitlab and nginx

This commit adds service resource blocks for both gitlab and nginx.
These are necessary as we are notifying nginx and gitlab to restart
after rendering templates files for each service.
Add gem_binary option to gem_package resource

This commit adds the gem_binary path to the gem_package resource block.
This is necessary so that when gems needed for gitlab are installed,
they are installed in the ruby gems directory created by the ruby we
build during the chef run.