Support for multi-tenant operations

[moolitayer]

There are going to be cross tenant apis and we would need to have some support for those in clients, currently created with one tenant in mind.

[jshaughn]

We are developing some cross-tenant endpoints in the REST API. Clients should likely just leverage the offered services (as opposed to making multiple single-tenant requests and aggregating client-side). Thee are targeted for admin level users with access to several tenants. MT fetch of Alerts/Events has been added the REST API, see [1]. Requests for other services can be discussed...

[1] https://issues.jboss.org/projects/HWKALERTS/issues/HWKALERTS-188