Version 70.   ***WIRING CHANGE***

This changes the pins for the ZProbe wiring to allow the ZProbe
to be used with the Duet and with the Duet+expansion board without
changing the firmware.  The new Duet expansion header pins for
the Z Probe are:

pin 2 >  .........................   < pin 50
pin 1 >  ...................ST....   < pin 49

S is the ZProbe signal output.  T is the trigger/modulator input.  S goes
to Arduino pin A10 and T goes to D52.
Version 0.71.  This has all the drivers in and active for the Duet expansion
board for multi-material printing.  It should (!) also work on a standard Duet with
the only strange behaviour being that you get funny temperatures for the non-existent
heaters. Note that you now have to define and select tools:

M563 P1 D0 H1 ; Define tool 1 to use drive 0 and heater 1
G10 P1 S185 R100.0 ; Set active and standby temperatures for tool 1

T1 ; Select Tool 1
M116 ; Wait for all temperatures

Don't use M104 and M109.

The first line, and possibly the second, could go in config.g.  The third
and fourth go in your G Code program.  See: http://reprap.org/wiki/G-code
Version 0.72.  MAC address can now be set dynamically.  See
http://reprap.org/wiki/G-code#M540:_Set_MAC_address
Minor tidying, and making tool change actually do what the docs say...
Fixed compatibility between the Webserver class and reprap.js so that multiple temps
don't get read as X Y Z etc.
Merge branch 'duet' into jason_duet