updated fork feature to use gitlab-shell for v5 of gitlab

app/contexts/projects/fork_context.rb

app/controllers/projects_controller.rb

app/models/ability.rb

app/models/forked_project_link.rb

app/models/project.rb

app/observers/project_observer.rb

app/views/projects/_clone_panel.html.haml

config/routes.rb

db/migrate/20130319214458_create_forked_project_links.rb

db/schema.rb

features/project/fork_project.feature

features/steps/project/project_fork.rb

lib/gitlab/backend/shell.rb

spec/contexts/fork_context_spec.rb

spec/factories/forked_project_links.rb

spec/lib/gitlab/backend/shell_spec.rb

spec/models/forked_project_link_spec.rb

spec/models/project_spec.rb

spec/routing/project_routing_spec.rb