add support for signing messages in compressed format

...this is the standard way to sign messages in bitcoin-qt. Note that the
format of a compressed signature, for messages, is quite distinct from DER
format, which is used in transactions. This commit also adds support for
recovering the public key from a signature, which is necessary for this. The
code for public key recover is taken from bitcoinjs-lib.
paypro: misc example changes.
paypro: replace old server address.
paypro: example - show raw hex when receiving Payment.
Merge pull request #476 from chjj/paypro_example_misc

Paypro example misc
add AuthMessage and fix browser tests
generalize version numbers
fix browser tests
setting networks.livenet as the default for WalletKey
Merge pull request #475 from maraoz/add/AuthMessage

adds AuthMessage and fixes browser tests
Merge pull request #478 from manan19/walletkey-params

setting networks.livenet as the default for WalletKey
Merge pull request #459 from ryanxcharles/feature/message-signing

add support for signing messages in compressed format
fix merge