Reserve new UID range for OEM.

Brillo will need to run new native system services, so reserve
a reasonable UID range to accomodate them. Having 1000 UIDs will
allow us to sub-partition this range if needed.

The range can be used by any OEM, not just Brillo, so name it
accordingly.

Bug: 22555869
Change-Id: I752428ee5025bf064a35ecbe6da50c041d87b724