More improvements for bip32

Previous api was breaking access to bip32key.getKey() for public keys, since internally the key was stored differently (as byte array instead of ECkey), forcing special casing in higher level api. Also it would make it awkward to get the bitcoin addreass from a public bip32key since we couldn't do bip32key.getKey().getBitcoinAddress(), also breaking Wallet interface.

These changes (most in [0a7914f] with [0291fc5] and [5107030] adding some polishing and fixes) fixes this problems.

Other improvements are included:
 * Added bitcoin addresses from test vectors into the mocha test [d7a0e0b]
 * Fixes one case of a variable that was being stored globally by error [5107030]