* add multiaccount support
add multi account ImportPrivateKey and StoreAccount
test derivation from normal keys
* add multiaccount to mobile pkg
* use multiaccount params structs from the mobile pkg
* move multiaccount tests together with the other lib tests
* fix codeclimate warning and temporarily increase methods threshold
* split library_test_utils.go to avoid linter warnings
* update master key generations using "Bitcoin seed" as hmac key following BIP32
* use `"mnemonic" + passphrase` as salt for pbkdf2 following BIP39
* test generated addresses and compatibility with BIP44
* check generated public keys
* test children private keys
* update MasterKey to be a constant
* don't export salt and masterKey constants
* use `crypto.FromECDSA` to get the hex representation of the priv key
* use empty pwd for the generation of the BIP39 seed, keeping pwd to encrypt keys
* add comment before the seed generation with empty passphrase
Andrea Franz
Pedro Pombeiro
Victor Farazdagi