Add support for blockstoragev3 volumetype encryption operations such as:

• Create an encryption type.
• Show an encryption type.
• Show encryption specs item.
• Update an encryption type.
• Delete an encryption type.

The code for this PR is also related to the effort mentioned in the following issue: #649

Links to the line numbers/files in the OpenStack source code that support the
code in this PR:

1. Create an encryption for a volume type:

   • API Docs
   • Code

2. Update an encryption for a volume type:

   • API Docs
   • Code

3. Delete an encryption for a volume type:

   • API Docs
   • Code

4. Show an encryption for a volume type:

   • API Docs
   • Code

5. Show an encryption spec for a volume type:

   • API Docs
   • Code