According to LinuxCNC, G5 should throw an error if the current plane mode isn't XY.

* Add Max7219 LED Matrix Debug Support

The Max7219 8x8 LED Matrix's are very helpful for debugging new code.
And for that matter, just trying to maximize printer settings without
causing stuttering.

The displays are very inexpensive (under $2.00 with shipping) and
provide a lot of help when trying to debug complicated code.

* Try to keep Makefile up to date.

When M405 is used it changes 'volumetric_multiplier[FILAMENT_SENSOR_EXTRUDER_NUM]' value. When M406 disables M405 it leaves the value unchanged.
This PR applies 'calculate_volumetric_multipliers' in M406 instead of resetting it to 1.0 because M200 may not be compatible with M405 hence I'm sure to restore anyway with correct value.

When switching noozle and extruder but these operations are done by the same servo in 'setup' function there is a unnecessary call

* Disallow filament change while paused

* Use kinematic movemements in pause_print and resume_print

Axis would only move when homing.
Bug introduced in 91841d75c9.
Fixes #6956, fixes #7050 and fixes #7291

Connected as described at http://printrbot.com/shop/led-strip/

Based on patch by Kelly Anderson <kelly@xilka.com> at
http://www.xilka.com/printrbot/marlin/1.1.4/20170707/

Without this...  The LSF won't work because none of the sampled points
in this code block get added.

We can save more and a pile of RAM by eleminating the eqnBVector and
EqnAMatrix arrays next.

Fixes #7250

Addressing #7227

Sends pre-defined string as action command when printer is kill.