Visibility fixes

Fix function visibilities for some ERC20, ERC721 and ENS functions

Last before refactoring

It's a last update before refactoring for 2.0 version with breaking API changes

Added:

• Tx pool tools (Infura has no access to Tx pool, be aware)
• ERC721 mapping to native Swift class

Modularity

• Start splitting to modules
• Preliminary ENS support
• Fix formatting in scientific fallback mode

XCode 10

• Update dependencies for XCode 10
• May require Cocoapods 1.6 beta

EIP681

• Implements EIP681 code parsing
• Fixes initialization of non-checksummed Ethereum addresses
• !!! IMPORTANT !!! changes default passwords for all the keystores

Password derivation degradation fix

improve performance of Scrypt KDF