The purpose of this patch set is to provide the end users with
the following functionalities:
1. Create volume type resources, only admin is able to create volume type
2. Show details for a volume type by id
3. List volume types
4. Update a volume type, only admin is able to update volume type
5. Delete a volume type, only admin is able to delete volume type
Change-Id: I6e3188018eff6db155ec02dbd2af6aefc0363df9