relax assumption that HD seeds are 128 bits
relax assumption that HD seeds are 128 bits

cleanup
Update HD wallets todo list.
Auto-upgrade to HD when fetching a change address.
Make DumpedPrivateKey serializable, so that it can be used to pass around keys between loosely coupled application components.
Fix a payment protocol unit test that had a forgotten @Test annotation and thus didn't actually work.
Fix ECKey.equals() and toString() to also include encryptedPrivateKey. Convert to Guava and consolidate at bottom of class.
Add ability to prefix or postfix currency codes when formatting coins. Defaults are BTC, mBTC and µBTC.
Coin.toFriendlyFormat() includes denomination (BTC). This saves a lot of string concatenation code.
Merged changes from upstream