Status LED logic needs to improve

[brian-r-calder]

The status LEDs' status isn't terribly logical, and are subject to some potential confusion. For example, if the SD card becomes full the logger will switch on the blue and green LEDs, but if you're capturing motion data, the "data writing" flash on the blue LED is sufficiently frequent that it looks as if the blue LED is permanently on, and the "normal" status (green LED on) makes it indistinguishable (at least to the casual observer) from "data writing".

Similarly, the "initialising" state (flashing green) never actually flashes since (a) the status doesn't get updated until the system is fully booted, and (b) the flashing is done through the run-loop, which doesn't start executing until the logger's fully booted. Therefore it's a wasted state and the logger looks dead for a disturbingly long time before it shows and blinkenlights.

Therefore:

1. Rationalise the colours and flash sequences so that the different states are clearly distinguishable.
2. Fix the initialisation sequence to use something that brings the LEDs on immediately and in a distinguishable state so that the logger shows signs of life as soon as possible after the power is applied.