Improve power consumption

[kroesche]

The firmware could be modified to place the MCU into a lower power consumption mode during the "delay" times between sampling. It can be made to wake on interrupt from CAN interface, or based on a timer for sampling. Right now it just uses polling delays. I believe that the LTC chips can also be made to use less power when idle but needs further investigation.

During the time when there is no CAN bus activity, I dont see the point in continuing to sample at all since there is nothing to read the sample. Therefore I think having a timeout such as 10 seconds after last message, then quit sampling and go into a lower power state. This is likely the time that the vehicle is parked and the system is just being sustained from the 12V battery which is slowly draining.