Merge pull request #5 from xeroc/master

added pthread to cmake
Network functionality improved, code somewhat dirty now though.
Move to vitalik's PoW...
Vitalik's diff changes.
Move to obscure's Hello format.
Back to how it was.
Log output.
Move to agreed network format.
GetChain fix.
Slightly more error resistant.
Peer discovery just-about safe, though you'll end up with a lot of
peers.
DONE: Connect default should be drop-down and populated via web api.
Rename of Main - MainWin.
* Kill peers when too many
  - Respect idealPeerCount.
  - Peer network traversal for peer discovery.
  - Check peer utility (useful transactions & blocks passed) for when
dismissing.
  - Respect peer count & dismiss/collect/stop listening for peers as
necessary.
Optimised network;
verbosity levels;
peer server mode;
configurable peer count;
more options in cli client.
Manage GetBlocks properly; should work for when > 256 blocks away.
Use GetTransactions on connect & respect it. DONE
Vaguely proper parameters.
Only debug version has a lower difficulty for now.
Threads linking now.
Respect and handle capabilities.
- Peer-servers should never kick eachother off.