[WIP] New generic interface for smartcontracts

[AntonMeep]

A work-in-progress new interface for any kind of smartcontracts + reworked wallet interfaces
It's features:

• Infinitely extensible - no unnecessary constraints are placed on any component, everything will be composed of simple and clear interfaces
• Will easily support uncommon scenarios - multi-sig wallets, highload wallets with no seqno, and so on and so forth
• Hides private keys from the pesky developer - I'm trying to make it as hard as possible for the end dev to misuse keys: leak them through a stupid object mapper in an api, flash it in the logs with a toString(), etc.
• Actually handling private key as a luxury, not a necessety - it will be possible to query information about contracts, such as walletseqno and such without actually needing to know their private key. First of all this will make it possible to only request user's authorization when actually needed (wallet apps) and second of all it will enable developers to use the same API for both already deployed and yet-to-be deployed contracts