Give names to threads for debugging purposes.

src/net/sf/briar/android/AndroidExecutorImpl.java

src/net/sf/briar/invitation/Connector.java

src/net/sf/briar/invitation/ConnectorGroup.java

src/net/sf/briar/lifecycle/ShutdownManagerImpl.java

src/net/sf/briar/lifecycle/WindowsShutdownManagerImpl.java

src/net/sf/briar/plugins/PollerImpl.java

...sf/briar/protocol/duplex/DuplexConnectionFactoryImpl.java

.../briar/protocol/simplex/SimplexConnectionFactoryImpl.java