Add get_fields method to orm.Entity
Add class `Model` to module `robottelo.entities`

This new class represents a "Model" entity in the Satellite application. For
reference material, see `apidoc/v2/models` on a Satellite deployment.
Merge pull request #934 from Ichimonji10/entities

Add class `Model` to module `robottelo.entities`
Merge pull request #925 from elyezer/orm-get-fields

Add get_fields method to orm.Entity