This change makes the choice of serial port configurable so that
wireless capability can be easily added by connecting Bluetooth modules
(such as BlueSmirf or JY-MCU) to the expansion port pins.

fixes #246
Added statements to set the limit switch positions to the maximum travel if homing in the positive direction as well as bed center at (0,0) if defined.
Relocated code based on feedback.

Added statements to set the limit switch positions to the maximum travel if homing in the positive direction as well as bed center at (0,0) if defined.

Conflicts:

	Marlin/Configuration.h

motor current and microstepping pins.

HOME_POS is now always where the endstop is and can be outside the limits.
The limits are now defined by MIN_POS and MAX_POS rather than HOME_POS and MAX_LENGTH.
The Z is axis now homed first if direction is away from the bed.

Saguinololu limit pins change from MIN to MAX according to the homing direction.

Turning off the protection might be beneficial to those who want to do fast and long reversals.

Changed SLOWDOWN. IF this does not work ok OLD_SLOWDOWN is the old algo.

Moved the PID_dT in the Ki and Kd calculation from the configuration.h to temperature.cpp

+ Removed most explicit pathnames, use the standard make "VPATH" to let
make find the files for itself.

+ Added a "hardware variant" variable that allows compiging Sanguino and
Gen7 as well as "generic" arduino.

+ Allows overriding the MOTHERBOARD define from the Makefile

+ Removed the 'preprocessor' bit that wasn't needed, now just "include" the
files that are needed, since it allows gcc to show the right file/line
when displaying error/warnings.

+ Uses gcc's own dependency generator to generate the .d files, and
and include these instead of self-patching the makefile

Signed-off-by: Michel Pollet <buserror@gmail.com>

V1.4 moves thermistor power to the always-on 5v line.
The BOGUS_TEMPERATURE_FAILSAFE_OVERRIDE is no longer
needed on this board.  Add a new motherboard type to
support this feature.

Included AD595 calibration options. (daid)