ccoin-agent-py: colored coin toolkit

[Alex Mizrahi]

Initial version of colored coin toolkit for Python is available here:

https://github.com/bitcoinx/ccoin-agent-py

Right now it is a very basic demo which fetches transaction data from bitcoind to initialize colored coin database.

But we are going to develop it into a fully functional wallet client (aka NGCCC).

Architecture corresponds to 'theory of colored coins' ideas and enables pluggable color kernels.

Demo includes only classic order-based coloring, but you can add support for other coloring schemes simply implementing a color definition class, like this:

https://github.com/bitcoinx/ccoin-agent-py/blob/master/src/colordef.py#L15

This architecture also encapsulates traversal strategy in Builder class and blockchain access method on BlockchainState class.

Demo implements only full scan builder (which does full scan of blockchain), but it is possible to implement a builder which would use external database (ABE) to speed up traversal.