Optimizing aggregation and fixing bug in staff team listing route.

 - In `server/router/routes/staffTeamList.js` a match was needed in order to restrict the aggregation only to users with `role` equal to `volunteer`.

 - Optimizes aggregation calls for each request by caching the match and group query objects passed in.
Fixing bug in volunteer deletion route

 - Two problems existed:
   - `delete req.session.volunteer` needed to be `delete req.session.user.volunteer`
   - `role` property in both database and session needed to be set
Consolidates authentications files, creates config file

 - Now only a single auth.json file needs to be added to the project root which contains subdocuments for "database" and "email". `auth.json` is now in our `.gitignore` but there is a sample file `auth.json.SAMPLE` which is available.

 - Adding default static configuration file which is passed into the `app.locals` call in `app.js`

 - Adding default allowed zip codes to config file which are only used if no document is returned from the zips collection.