Improvements and Fixes for Edge Cases in X.509 Certificates (Continuation)

[akarabashov]

This is a continuation of Issue #535 , here are
improvements and fixes that were either not included in the previous issue's scope or were transferred from the scope of that issue.

Current Behavior and Proposed Fixes

Current behavior	Proposed Changes	Comment
1. It is possible to add the root certificates with the same subject and SKID but with a different VID field	After adding the first root certificate with a specific VID, all subsequent certificates that are added with the same subject and SKID fields must have the same VID field
2 Only original proposer account of a Root cert with the given Subject+SKID can propose another root cert with the same Subject+SKID	Any Trustee can propose any root certificates
3. If a Root or Leaf certificate is revoked, there is no way of un-revoking it or proposing it back.	For Root and Non-root: Need to be able to re-add after revocation (soft-delete) or remove