NAWQAAN-162

* Added long term mean line
* Calculating from data, will sub in Casey's data later
* Unable to do hover yet, need to either be clever or hack around a bit

This is good to get some eyes on it, though task is not completed until hover is done.
I just want it to be big so it is not in the time range of the plot.  I don't know how flot would react to max_value.