Split Ticket Service & Client

This is a beta release of the split ticket buyer service and client. Please
read the instructions for joining the beta.

Mac version provided by @girino.

Changelog for vesion 0.6.0

Bump protocol version to 3
Service can now be restarted without stopping the process by receiving a
SIGHUP signal
Service now shuffles participants after defining the actual contribution
amounts of a new session
Switch to using pool fee contribution proportional to contribution to the
ticket (previous versions used a fixed pool fee by participant)
Add a beta participation disclaimer before starting to wait for a session
Updated to testnet3
Fix GTK deprecation warning in GUI
Fix socket leak in websocket waiting list watcher
Add --version argument to service
Various other small tweaks and fixes