Add advanced rbacdefinition validation

[sudermanjr]

Combining the requests of both #99 and #101, it would be very beneficial to end users to have some extended validation of the rbacdefintion. This issue will serve as a proposal and tracking issue for that request.

Things to be validated:

• Namespaces referenced by rbacdefinition currently exist
• Roles/ClusterRoles that are referenced in rbacdefinition currently exist
• ServiceAccounts referenced by rbacdefition do not exists, or if they do, let the user know? Defined by results of Verify behavior around pre-existing service accounts #84

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.