Move models under their corresponding API modules.

[obmarg]

Most of the models in Kazan correspond with a particular API & API version. For example Kazan.Apis.RbacAuthorizationV1.list_role_for_all_namespaces returns Kazan.Models.Rbac.V1.RoleList.

I'm thinking it would make more sense if models were grouped with the APIs that they correspond with. For the above example this would mean Kazan.Apis.RbacAuthorization.V1.list_role_for_all_namespaces would return a Kazan.Apis.RbacAuthorization.V1.RoleList.

This would make grouping documents as suggested in #20 a bit easier - the groups could correspond with the individual APIs.