Spindle/coolant rare bug fixes. Free more flash.

[new] Altered the way default settings are stored and restored. Saved about 300 bytes(!) of flashed size. Should free up enough for certain configurations of CoreXY machines.

[fix] When the optional M7 mist coolant IO was enabled, coolant overrides was not disabling correctly.

[fix] Coolant override states was not restored correctly after a parking motion in certain situations. It would restore programmed state, rather than current overridden state.

[fix] Now allow coolant overrides to operate during jogging motion.

[fix] Invert control pin mask typo.

[new] Added a new build info feedback mechanism for enabling the safety door input pin.

doc/log/commit_log_v1.1.txt

@@ -1,3 +1,30 @@
+----------------
+Date: 2018-06-09
+Author: Jon
+Subject: Fix apparent error in restore masking that causes the call to coolant_set_state to not re-enable the mist (M7) output if it was previously enabled. (#469)
+
+
+
+----------------
+Date: 2018-04-06
+Author: Sonny Jeon
+Subject: Updated instructions in fit_nonlinear_spindle.py
+
+- repl.it has changed since the last time fit_nonlinear_spindle.py was tested. Updated instructions.
+
+
+----------------
+Date: 2017-08-01
+Author: Sonny Jeon
+Subject: Improved fix for rare lowering feed/rapid override bug.
+
+[fix] In the previous hot fix, there was still (rarer) potential for
+very small floating point errors incorrectly handle an override
+deceleration and crash Grbl. Re-factored the if-then statement in terms
+of speed changes, rather than distance, to completely eliminate the
+issue.
+
+
 ----------------
 Date: 2017-07-31
 Author: Sonny Jeon