txsplain edits for EnableAmendment, etc.

[mDuo13]

• Fixes time zone discrepancy in dates parsed from different formats
• Differentiates transactions from pseudo-transactions
• Adds custom descriptor for EnableAmendment pseudo-tx:
  • Indicates whether the tx represents gaining a majority, losing a majority, or enabling an amendment
  • For the majority-gained case, estimates when the amendment will become enabled