Major re-write for SMT v0.6 Rev A board

Changes to much of the code to support the new TCS34725FN I2C light
sensor device, and the new 5 LEDs for user bar graph goal feedback. The
new sensor provides 16bit per channel of data  and is currently set to
cover 1 lux to 100+ klux. Code includes some bit tricks to reduce that
to 10bits per channel at the cost of reduced resolution as the lux
increases to large values (similar to the behaviour of the previous LDR
sensors). The TCS34725FN device is using low power management between
readings, but it may be better to fully power the device down.
TCS34725FN also supports changing integration time and sensor gain,
these may be used in future build to extend the light sensitivity above
and below the current range.
Comment correction
Don't fail if header is missing some stat

Header stat data can be prone to change from time to time so don’t bail
unless some critical data is missing.
Remove 20k lux calibration

Calibration of 20k lux is un-necessary for primary use case. Removing
it frees up some much needed program space and makes calibration
simpler.
Lux scales update

New visual lux graph line positions for 2.5k, 5k, and 10k lux from the
new sensor and data format.
Calculate day phase and transmit with commands

Generates the day phase using the sync machine and transmits it along
with the standard device commands to keep the day phase in sync.
Update to 2.5k, 5k, and 10k lux calibration

New values for lux calibration for the new SMT light sensor and data
compression.
Remove un-needed 20K calibration data
Rework SMT colour sensor processing

Tries two levels of exposure gain, x16 and x1, to capture more data in
dark conditions. Includes compressing data to 10-bits per channel for
the two exposure settings.
Refactor goal_update to a separate routine
Day phase improvements

Remove manual day phase commands and replace with setting phase during
comms cycle with two bytes while synching.
Remove 20k lux calibration comms and function
Changed variable used for header_block calc
Corrected data needed to be copied at first init
Eagle CAD board and schematic for SMT v0.6
Eagle CAD board and schematic for SMT v0.6B

Revision B has some minor label corrections and larger drill holes for
the 3.5 SMT jack socket component.
Initial enclosure work

Blocking out volume needed for hand build prototype
Adding more detail to device volume
Revert "Adding more detail to device volume"

This reverts commit 9381a92e6241ea29a37aab7485646c7582f03154.
Revert 9381a92..73068e1

This rolls back to commit 9381a92e6241ea29a37aab7485646c7582f03154.