Removed methods that are no longer needed for Java 6, moved the remaining method into the utils directory.

"synchLock" will become confusing when we have lots of objects with "sync" in the name.

- replaced use of Object instance mutex with a private final Lock object
- replaced Object signaling with specific condition signalling

DuplexOutgoingSession flushes its output stream if it's idle for a
transport-defined interval, causing an empty frame to be sent. The TCP
and Tor plugins use a socket timeout equal to twice the idle interval to
detect dead connections.

See bugs #27, #46 and #60.

We don't need two separate executors for long-running IO threads.

This may have been the cause of bug #69. Removed the wait-for-shutdown
code in DroidtoothPlugin that was added to attempt to avoid that bug.