This is a nice VM, it has an interesting stack items model, better separation
of elements from stack implementation, simpler stack implementation and a bit
nicer opcode implementation mechanism. At the same time it lacks so many
features and is so differing from our current VM (that is closely tied to the
compiler) that it makes its code very hard to reuse for master's VM
improvement.
Also, some differences are non-obvious to judge in terms of better or
worse. Stack item model seems to be more extensible, but at the same time we
know very well what kind of stack items we have and this doesn't change a
lot. Slice-based stack is simple but it's hard to say which one would perform
better for real-world smart contracts (it has different tradeoffs in
operations complexity).
Based on that, I'm dropping it. Some ideas will be reused during VM
refactoring, but no more than that. Refs. #307.
And drop associated _pkg.dev remnants (refs. #307).
Original `dev` branch had two separate packages for public and private keys,
but those are so intertwined (`TestHelper` subpackage is a proof) that it's
better unite them and all associated code (like WIF and NEP-2) in one
package. This patch also:
* creates internal `keytestcases` package to share things with wallet (maybe
it'll be changed in some future)
* ports some tests from `dev`
* ports Verify() method for public key from `dev`
* expands TestPrivateKey() with public key check
It's the same implementation that we have in pkg/crypto (based on
https://github.com/vsergeev/btckeygenie) but with tests preserved. I don't see
any reason to port tests from it because even the pkg/crypto copy should go
away to fix#245.
With associated test and drop duplicating Uint160 implementation from
_pkg.dev. It doesn't seem to be used in pkg code at the moment, but still it
can be useful. Refs #307.
The idea here is to preserve the history of `dev` branch development and its
code when merging with the `master`. Later this code could be moved into the
masters code where appropriate.
