KeyChainGroup's currentAddress/freshAddress vend P2SH addresses for married keychains
Married HD wallets: KeyChainGroup currentKey/freshKey will throw an exception
Married HD wallets: add a method to marry the keys

A new method addFollowingAccounts is intended to "marry" a given list of extended public keys to the zero account key of the active keychain.
Merge branch 'mw-shadow-keychain' of https://github.com/troggy/bitcoinj into mw-shadow-keychain