Support DOMAction-level routing

Support DOMAction-level routing

We have a distinct use case where we want to route actions across
a system. In this scenario, a next hop provider registers itself as the
local provider with the appropriate cost.

This capability is also exposed as the simplest way of registering
binding-level implementations -- where we want to register to all
actions on the operational datastore.

Add explicit documentation around how how the arguments are interpreted
and teach DOMRpcRouter about wildcards -- similar to how it deals with
RPCs.

JIRA: MDSAL-681
Change-Id: I6daf70b28347fab88c8dc467fce267d8ba71e57d
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>