Replace manifest services with lists of env variables

Removes bindings to user provided services for new application
deployments and sets the expected environment variables to `null`.

Listing variables in the manifest allows us to only inject secrets
used by the app. `null` is not a valid value for a variable in a
CloudFoundry manifest, so if any of the keys don't have a match in
the credentials file `cf push` will return an error and stop the
deployment.

manifest-api-staging.yml

@@ -2,14 +2,7 @@
 
 inherit: manifest-api-base.yml
 services:
-  - notify-aws
-  - notify-config
   - notify-db
-  - mmg
-  - firetext
-  - hosted-graphite
-  - redis
-  - performance-platform
   - logit-ssl-syslog-drain
 
 routes: