explorer: Better Transaction Details

[winder]

Better transaction details. The current version prints raw msgpack data of the transaction, this could be more readable. Some ideas:

• Formatted section for common transaction headers (sender, receiver, fee, type, first-valid, last-valid, signature)
• Custom formatting for each txn type:
  • pay, asset, app, keyreg, etc
• Compute the txid
• Convert the sender / receiver from b64 encoded string to the Algorand formatted address string.
• Attempt to format the note using known common encodings (i.e. JSON, Text, Base64, Hex Viewer)