Support max31855 thermocouple over spi.
Limit SPI transaction to 16 bits.
Some error handling cleanup.
Changed config parameter name.
Added buffer for averaging of measurements to improve PID robustness.

Also ignore occasional failed measurements from the thermocouple.
Formatting changes.
Added G30 simple Z probe, will probe for Z at current XY and report how far the probe moved down
Merge pull request #380 from wolfmanjm/feature/z-probe

Added G30 simple Z probe, will probe for Z at current XY and report how ...
Merge remote-tracking branch 'upstream/edge' into edge
Add Z probe to M119
Change G30 to return to originalpostion after probe
G30 Znnn will stop probe on hit and set Z to nnn
Merge pull request #381 from wolfmanjm/upstreamedge

Add Z probe to M119
Merge remote-tracking branch 'upstream/edge' into edge
Save arm specific options with M500 disspaly with M503
change the arm solution options to a map, and optimize how they are set and get
add delta knowledge to z probe so deltas can be probed
Merge pull request #382 from wolfmanjm/upstreamedge

Save arm specific options with M500 disspaly with M503
Merge remote-tracking branch 'upstream/edge' into edge
Merge pull request #378 from hakalan/thermocouple

Support for MAX31855 thermocouple
Merge remote-tracking branch 'upstream/edge' into edge