Adding azure provider implementation for schema service

These set of changes introduce azure implementation of schema service.

Testing

Unit tests have been added for required classes.

Integration tests: pending

What might change in future:

Data partitioning in azure cosmos db: currently data from all the tenants is being stored in a single cosmos db instance, partitioned by the dataPartitionId of that tenant. This model might change in future.

@danielscholl , @dkodeih FYI.