CMerkleBlock class and wire messages

[cpacia]

I've had this code for a while, figured I'd submit it. I've run it on the network and it has worked, but you'll definitely want to review it.

Also, to use this code, the version in the msg_version would need to be bumped and the relay boolean added.

[petertodd]

Awesome, thanks!

I've really busy for the rest of this week, but I should get a chance to look at this next week.

[petertodd]

Did you try the unit tests? Just tried them and both python2 and python3 unit tests seem to be failing with this change.

You can run them with the following command:

python -m unittest discover && python3 -m unittest discover

[cpacia]

I only ran the tests I added separately. Not sure why it would cause other tests to fail as no other code was modified, but I'll take a look.