This allows easier reuse of opcodes and in some cases allows to eliminate
dependencies on the whole vm package, like in compiler that only needs opcodes
and doesn't care about VM for any other purpose.
And yes, they're opcodes because an instruction is a whole thing with
operands, that's what context.Next() returns.
* support VM to pass method and arguments to a script.
* added support for type assertions in smartcontracts.
* added native vm support for print.
* moved VM API packages to vm -> API
* reverted the native Print opcode in favor of runtime.Log
* added support for registering custom interop hooks in the VM.
* Updated README
* Updated compiler with @OPTIMIZE tags
* Moved more tests to VM package.
* optimized and refactored compiler and vm API
* updated README with new smartcontract apis
* bumped version
