Support versioning in ket format

Is your feature request related to a problem? Please describe.
Adding breaking changes to the ket format.

Describe the solution you'd like
The main goal of the task is to add a version field to the ket format.
We would like to have the ability to add breaking changes to the ket format but keep supporting previous formats which are already used by our users.
We will use SemVer for versioning.