* 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
Samuel Hawksby-Robinson
Pedro Pombeiro
Andrea Franz