(POOLER-181) Separate Dashboard from api

Allow the dashboard to run separately from the API, so that the
dashboard can be scaled appropriately.

Note - this implementation actually co-runs the api in the dashboard
instance to re-use the api code for the dashboard endpoints and other
v1 endpoints collecting the operating information.

spec/integration/dashboard_spec.rb

@@ -27,7 +27,7 @@ describe Vmpooler::API do
 
     before(:each) do
       expect(app).to receive(:run!)
-      app.execute([:api], config, redis, nil, nil)
+      app.execute([:dashboard], config, redis, nil, nil)
       app.settings.set :config, auth: false
     end