Scale UI controls on tablets
Added autopilot mode - show random trails when idle for 10 seconds

Autopilot mode is engaged when you first start the DotField server, and
is automatically disengaged as soon as anybody interacts with it.
After 10 seconds of no interaction, autopilot mode will start again.
The length of idle time you have to wait before autopilot engages can
be set by editing config.json (see config.json.example for example)