Further work on PID settings UI

Finally managed to make the layout details spinner controls work fine,
the bootstrap-spinedit library is not very easy to use - returns
string values for numbers...
Arduino sketch update: add command ack name

The arduino controller now adds the command name to ack packets
so that the server knows what it is acknowledging for.
PID settings support

Controller PID settings can be read/saved/modified, including while
running. Updated link Manager to use built-in Backbone events rather
than my own class.
Add touch support for power control slider

Now works fine with finger drag - and page does not scroll -
Detect controller unplug on the server

If train controller is disconnected, then a disconnect signal is sent to the web
interface - was not detected before.
Bugfix - when power=0, progress slider did not get updated

was testing for value, not for isNaN...
Don't glow non-clickable thumbnails
Link establishment more robust

The server now waits until it gets a steady flow of json input
before sending a "link established" message. "Connect" button on the
front end uses "warning" color while trying to connect. Various bugfixes.