goal clerk inspect: more base32+checksum fixes

[zeldovich]

Actually display the checksum for multisig PKs; also display txn Sender,
Receiver, and CloseRemainderTo using the same address encoding; and fix
the counter for displaying multiple txns in a file.

[Karmastic]

Since we have some time for this, can you add a test or 2 that will catch changes to types that will cause your built-in validation to fail?

[zeldovich]

Since we have some time for this, can you add a test or 2 that will catch changes to types that will cause your built-in validation to fail?

I added some positive tests. What did you have in mind for catching failures? I believe it requires either changing the SignedTxn type (or its children, like Transaction), or breaking the code in inspect.go. Neither seems like it can be cleanly localized in a unit test, and I don't think polluting the real SignedTxn or Transaction types with extra test-only fields is worth it for this test.

[Karmastic]

Thanks - looks great. The tests should catch struct changes early.