Backend Multi-Campaign Model

[Astor]

Implement a top level Campaign Model for the CAMPY API.

Protocol for Managing a Campaign

1. Account creator is the owner of the top-level account.
2. Account owner may create many Campaigns.
3. Each Campaign maintains it's own contacts, volunteers, newsletters and encryption keys individually.
4. A Campaign may have the following states (Active, InActive, Archived)

Requires an update to the database to create the Campaign table and update the rest of the tables with the campaign_id relationship.