Wallets!

First of build-in crypto-wallets: Ethereum.

• Build-in ethereum wallet: send, receive, watch transactions history.
• Send supported tokens (ADM and ETH for now) in chat.
• HUGE performance improvements (core migrated to native code. yay!)
• Minor tweaks, like "Stay in" & "Touch/Face ID" options are moved to Account page.
• Some bugs fixed here and there.
• Swift 4.2