Bed auto Leveling change: Raise Z before homing

- Added "Z_RAISE_BEFORE_HOMING" for raising Z the defined distance
before homing. This is useful to avoid Z-Probe collision when hotend is
near bed.

- Fixed the issue of Z not going bellow Z_PROBE_OFFSET when
"min_software_endstops" is true.
Now the Z_PROBE_OFFSET is not set in Z_MIN_POS, it is added after
homing.

Marlin/Configuration.h

@@ -309,7 +309,10 @@ const bool Z_MAX_ENDSTOP_INVERTING = true; // set to true to invert the logic of
   #define X_PROBE_OFFSET_FROM_EXTRUDER -25
   #define Y_PROBE_OFFSET_FROM_EXTRUDER -29
   #define Z_PROBE_OFFSET_FROM_EXTRUDER -12.35
-  
+
+  #define Z_RAISE_BEFORE_HOMING 4       // (in mm) Raise Z before homing (G28) for Probe Clearance.
+                                        // Be sure you have this distance over your Z_MAX_POS in case
+    
   #define XY_TRAVEL_SPEED 8000         // X and Y axis travel speed between probes, in mm/min
   
   #define Z_RAISE_BEFORE_PROBING 15    //How much the extruder will be raised before traveling to the first probing point.
@@ -330,12 +333,7 @@ const bool Z_MAX_ENDSTOP_INVERTING = true; // set to true to invert the logic of
 #define Y_MAX_POS 205
 #define Y_MIN_POS 0
 #define Z_MAX_POS 200
-
-#ifndef ENABLE_AUTO_BED_LEVELING
 #define Z_MIN_POS 0
-#else
-#define Z_MIN_POS (-1*Z_PROBE_OFFSET_FROM_EXTRUDER)  //With Auto Bed Leveling, the Z_MIN MUST have the same distance as Z_PROBE
-#endif
 
 #define X_MAX_LENGTH (X_MAX_POS - X_MIN_POS)
 #define Y_MAX_LENGTH (Y_MAX_POS - Y_MIN_POS)