cleaned up 'water' program code

The command line program 'water' for controlling
the valves has been cleaned up.

  - better error messages
  - grouped together related code
  - eliminated use of a global variable
  - added more error checking
created schematic in Kicad

The schematic has been converted to Kicad.
No errors were found by the Electronic Rules
Checker (ERC).

Several features of Kicad helped make the schematic
simple.  It has the concept of "sheets" which allow
a sub circuit to be created and interfaced through
its inputs/outputs.  And this sub circuit can be used
repeatedly.  This made the driver circuit simple
since it was just eight copies of the same circuit.

Next the netlist needs to be created and then
the pcb can be designed.
reviewed MC34063 design, corrected calculations

The design of the MC34063 switch mode voltage
has been reviewed and the component values have been
adjusted according to the corrected calculations.
A Matlab script that performs these is included (mc34063.m).
detailed values for power supply circuit

Detailed operating limits have been added to
the power supply circuit for all component
values.
documented expansion capabilities

The system uses SPI to communicate with the control
groups which allows it to be daisy chained for expansion.
However the current design is limited to three control
groups with a single power supply.
Merge branch 'master' into build
new document build