policer: API policer selection by index

policer: API policer selection by index

Policer API calls were only by policer name. It is now possible to
select a policer by its index.
Some functionalities are also added to allow updating a policer
configuration and to refill its token buckets.
Some dead codes are being removed, and small fixes made.

Type: improvement

Signed-off-by: Maxime Peim <mpeim@cisco.com>
Change-Id: I4cc8fda0fc7c635a4110da3e757356b150f9b606