Add 4th extruder

Add 4th extruder

Add 4th extruder

Pull for divergence.

There’s no need to ask users to uncomment Max Endstop pins when they
have them. These will be set to -1 later if the endstop option is
disabled.

Hopefully this is helpful to organization and future expansion….

There’s no need to ask users to uncomment Max Endstop pins when they
have them. These will be set to -1 later if the endstop option is
disabled.

#1405 includes some changes to pins.h for a 4th extruder. This commit
applies those changes. It also deals with a possible problem with
SENSITIVE_PINS.

All the additions look proper. I can't think of any other extruder-count-related items that you might have missed. So, with some optimism, I will merge this for testing.

Hopefully this is helpful to organization and future expansion….

Add PID_dT in temeprature.cpp

Proposed fix to #1379. Printrboard I2C LCD support

Pins 2 and 3 are probably general-use pins, since the filament sensor
uses pin 2.

Diverged from origin

Diverged from origin

Replace instances of the number 13 with FILENAME_LENGTH where
appropriate.

Githun insert this line when i merge with actual Branch development...

Conflicts:
	Marlin/temperature.cpp

Borrow from Ultimaker to fix MAX6675 SPI conflict

Branches diverged

Changes to temperature.cpp from Ultimaker fork, intended to address
#1226 and #1227

Replace instances of the number 13 with FILENAME_LENGTH where
appropriate.

Formatting for code-folding plus minor style changes to less active
code.

Formatting cleanup of quiet sources