reflect the change from "mediaanalytics" to "mediametrics"

Also incorporates a broader access to the service -- e.g. anyone.
This reflects that a number of metrics submissions come from application
space and not only from our controlled, trusted media related processes.
The metrics service (in another commit) checks on the source of any
incoming metrics data and limits what is allowed from unprivileged
clients.

Bug: 34615027
Test: clean build, service running and accessible
Change-Id: I657c343ea1faed536c3ee1940f1e7a178e813a42

Divide policy into public and private components.  This is the first
step in splitting the policy creation for platform and non-platform
policies.  The policy in the public directory will be exported for use
in non-platform policy creation.  Backwards compatibility with it will
be achieved by converting the exported policy into attribute-based
policy when included as part of the non-platform policy and a mapping
file will be maintained to be included with the platform policy that
maps exported attributes of previous versions to the current platform
version.

Eventually we would like to create a clear interface between the
platform and non-platform device components so that the exported policy,
and the need for attributes is minimal.  For now, almost all types and
avrules are left in public.

Test: Tested by building policy and running on device.

Change-Id: Idef796c9ec169259787c3f9d8f423edf4ce27f8c