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

This should enable us to connect to contacts faster at startup and
whenever a new means of connecting becomes available.

The LAN plugin only accepts IPv4 link-local or site-local addresses.
This rules out LANs that use globally routable addresses (such as UCL),
but also reduces the chances of the LAN plugin making observable
connections across the WAN, which could reveal the social graph.

Both plugins will attempt to reuse the previous address and port only if
there's currently an interface with that address; this will avoid
unnecessary attempts to bind to nonexistent addresses.

Of course, not all devices support Bluetooth...

- add a UnixRemovableDriveMonitor.checkEnabled to pre-emptively check if it's loaded
- os.arch is always x86,x86_64 on windows, i386,amd64 on linux
- source: http://www.java-gaming.org/index.php/topic,14110
- we'll deal with freebsd support when we come to it, jnotify doesn't even do this atm

This way the tests won't show up as having run if they didn't.