Add API schema for v2.1/v3 quota_sets API

By defining the API schema, it is possible to separate the validation
code from the API method. The API method can be more simple.
In addition, a response of API validation error can be consistent for
the whole Nova API.

Partially implements blueprint v3-api-schema

Change-Id: I90c7a82a017cd67328f390c8a9bd0774d61139bd
Merge "Add API schema for v2.1/v3 quota_sets API"