Refactor DB Roles

[owine]

Refactor DB roles and roles that utilize a database.

Postgres

• [x] Add multiple instance support
• [x] Update Saltbox roles
• [x] Update Sandbox roles
• [ ] Create migration path

MariaDB

• [x] Add multiple instance support
• [x] Update Saltbox roles
• [x] Update Sandbox roles
• [ ] Create migration path

MongoDB

• [x] Add multiple instance support
• [x] Update Saltbox roles
• [x] Update Sandbox roles
• [ ] Create migration path

[owine]

Work on this moves to #119 and associated branch. Likely to just implement multi-instance support as a start. Migration path still unclear.

[saltydk]

Can we close this or is there still work to be done?