Using same IV in AES-GCM across multiple invocation of
encryption/decryption operations can pose a security risk. It can help
to reveal co-relation between different plaintexts.
This commit introduces a change to use part of IV as a monotonic
counter, which must be incremented after every AES-GCM invocation
on both the client and the device side.
Concept of patch version for a security scheme has been introduced here
which can help to differentiate a protocol behavior for the provisioning
entity. The security patch version will be available in the JSON
response for `proto-ver` endpoint request with the field
`sec_patch_ver`.
Please refer to documentation for more details on the changes required
on the provisioning entity side (e.g., PhoneApps).
