Prevent startup is cjdns is already running. Closes #317.

Before startup, it tries to ping existing cjdns instance. If ping
succeeds, cjdroute refuses to start.
Better names for ping-related variables.
Added sessionStats python script, fixed SessionManager_getHandles() to report correct handle numbers.
Merge branch 'startup-check' of https://github.com/m1kc/cjdns into next
fixed a crash-on-start bug caused by a leftover UDP socket.
added parameter to allow changing timeout for adminClient, set timeouf to 100ms for checking if cjdns is active already.