secrets should be associated with application deployment

[LincolnBryant]

Right now, secrets are a bit buried in groups. When we launch an app, we need to add secrets for certain apps. For example StashCache needs a cert and key, HTCondor needs a pool password. When a user goes to deploy an app, we may need an "Add A Secret" button next to "Install App". The readmes for each app probably need to be updated too