Defined service interface and models for discovered assets

AFDP-77
Added IP address field and removed discovery hint field.
Refactored the location of the service facade API to the service
module.
Implement integration tests for the new DiscoveredAssetService.

AFDP-78
Merge pull request #35 from ualerts-org/AFDP-1

Afdp 1 - Part One