Validation timing


Fix the validation timing problem.
    * Log whether consensus built a ledger we already had or were acquiring
    * Don't trigger an acquire for a validation for a ledger we might be building
    * When we finish building a ledger, try to accept that ledger
    * If we cannot accept a built ledger, check held validations
    * Correctly set isCurrent for untrusted validations
    * Add appropriate logging