Add webserver recipe and attributes.
Change the permissions of gitlab-rails dir, change location of the sockets directory.
Uploads directory change for permissions and ownershipt.
Move socket directory creation to unicorn section.
Add the notes about using external webserver to README.
Incorporate suggestions.
Merge branch 'non_bundled_server' into 'master'

Non bundled webserver support

Fixes #157

See merge request !199