Whitespace fixes, changes and corrections to the menu structure and text.
Whitespace fixes.
current_version.txt:
 * Added description of 7.3.2 and 7.3.1 firmware releases

Motherboard.cc:
 * Whitespace fixes
 * Changed error handling behaviour, more heater errors will cause the print to be aborted
 * Added heater errors

ThermocoupleDual.cc:
 * Changed error reporting algorithm, error codes are now returned and temperature value is passed by reference
 * Added error codes for communication error with the ADC chip

ThermocoupleReader.hh:
 * Changed error reporting algorithm, error codes are now returned and temperature value is passed by reference
 * Whitespace fixes

ThermocoupleReader.cc:
 * Changed error reporting algorithm, error codes are now returned and temperature value is passed by reference
 * Added error codes for communication error with the ADC chip

sd_raw.c:
 * Added fix for Rev H SD card read speed differences

Heater.hh:
 * Added error codes for communication error with the ADC chip

Heater.cc:
 * Added error codes for communication error with the ADC chip

Menu.cc:
 * Changed maximum preheat temperature to 280 for extruders and 130 for heated build plate

Menu_locales.hh:
 * Removed unused error
 * Slightly changed wording of existing heater errors
 * Added numbers to heater errors
 * Fixed print out formatting

TemperatureSensor.hh:
 * Added error codes

TemperatureTable.hh:
 * Fixed access to temperature tables allowing full tables to be accessed

TemperatureTable.cc:
 * Fixed access to temperature tables allowing full tables to be accessed
Fixed numbering of Heating Failure messages
Merge remote-tracking branch 'origin/height_stop' into height_stop