Use Passport (node module) for security abstraction

[kelfink]

@josephmfaulkner brought up an issue with relying on Cognito only. Using Passport would let us pick our own back-end authentication service. More write-up to come

[kelfink]

Four user roles make sense for now...

• Sys Admin -- global unrestricted access
• Neighborhood Admin -- has access to add/edit/remove(?) Priorities and actions for their assigned neighborhood(s)
• City Admin -- has access to add/edit/remove (for now) Priorities and actions for any neighborhood
• Public -- has access to see any Priorities and Actions from any neighborhood. -- no editing or sorting.