Add secret utilization data support in Barbican

The utilization data of secrets, for example, how many keys are created by a tenant/project, for which key type. how many GET-secret operation done per day/week/month etc, are very useful for key manager service monitoring and for service provider's billing purpose.

This effort is to add utilization data on secret creation and retrieval in barbican data model, and add a new API to query these utilization data, so that other 3rd-party monitoring tool can use them to generate secret usage metric.

The implementation of this blueprint should includes:
1) add appropriate counters for secret POST/PUT and secret GET operations in project
2) add optional counter for secret GET in secret object
3) add a new GET API for querying utilization data
4) capability to track usage metric in terms of a group of projects.
5) capability to limit secret & order quota in terms of a group of projects. group quota takes precedence over project quota.
6) new API document and user guide update