Jack transport: new features added

1. Jack Transport reposition
2. Jack Timebase slave
3. Changed Preferences->I/O UI
4. Jack restoring audio connections
5. Jack: changing parameters without driver unload
6. Bug fixes
I believe this is not safe to call from the RT thread. cs->end() will do a screen update.
For the record, cs->setPlayPos is responsible of the warning http://musescore.org/en/node/27721
setPlayPos calls setPos(), which then will emit posChanged. Since we are in a non UI thread, a queue is used to send the signal, and Qt is complaining because it can't put POS in the queue since the type is unknown for the meta type system.