[WFCORE-82] Add an additional warning to the schemas to point out that a correctly configured security realm is required for SSL.

This is not a backwards compatibility change as previously an invalid configuration would result in a failed server start-up due to a NullPointerException.
[WFCORE-82] Verify that the associated security realm does supply an SSLContext.
[WFCORE-82] Add validation for both attribute writes and the addition of the resource itself.