Dharitri blockchain base types, interfaces and builtin function names

It provides various types and constants referring to the Dharitri blockchain base implementation.

This functionality is designed to be minimal and to be used from both smart contract code and VM implementations.

It can be viewed as a collection of system specs, which hold for any Dharitri-related implementation. For example:

• Address - Dharitri addresses are 32 bytes long. This is the old SC address type, it holds the bytes on the heap. It is also used in the Dharitri Rust VM.
• H256 - same as address, currently used for transaction hashes.
• Flags:
  • Code metadata - a bitflag encoding the SC code metadata, as it is stored on the blockchain, and encoded in smart contracts;
  • DCDT local roles
    • as enum
    • as bitflags
  • DCDT token types