Fixed Z_PROBE_PIN pullup bug.

Documented some additional areas that should be addressed if Z_PROBE is
fully separated from Z_MIN or Z_MAX.
Fixed a documentation error in sanity checks. Servos start at 0 not 1.

Marlin/Conditionals.h

       #define ENDSTOPPULLUP_ZMIN
     #endif
     #ifndef DISABLE_Z_PROBE_ENDSTOP
-      #define ENDSTOPPULL_ZPROBE
+      #define ENDSTOPPULLUP_ZPROBE
     #endif
   #endif
 

Marlin/SanityCheck.h

         #error You must have at least 1 servo defined for NUM_SERVOS to use Z_PROBE_AND_ENDSTOP
       #endif
       #ifndef SERVO_ENDSTOPS
-        #error You must have SERVO_ENDSTOPS defined and have the Z index set to at least 1 to use Z_PROBE_AND_ENDSTOP
+        #error You must have SERVO_ENDSTOPS defined and have the Z index set to at least 0 or above to use Z_PROBE_AND_ENDSTOP
       #endif
       #ifndef SERVO_ENDSTOP_ANGLES
         #error You must have SERVO_ENDSTOP_ANGLES defined for Z Extend and Retract to use Z_PROBE_AND_ENSTOP

Marlin/stepper.cpp

 static volatile bool endstop_x_hit = false;
 static volatile bool endstop_y_hit = false;
 static volatile bool endstop_z_hit = false;
+static volatile bool endstop_z_probe_hit = false;
 
 #ifdef ABORT_ON_ENDSTOP_HIT_FEATURE_ENABLED
   bool abort_on_endstop_hit = false;
 #define DISABLE_STEPPER_DRIVER_INTERRUPT() TIMSK1 &= ~BIT(OCIE1A)
 
 void endstops_hit_on_purpose() {
-  endstop_x_hit = endstop_y_hit = endstop_z_hit = false;
+  endstop_x_hit = endstop_y_hit = endstop_z_hit = endstop_z_probe_hit = false;
 }
 
 void checkHitEndstops() {
-  if (endstop_x_hit || endstop_y_hit || endstop_z_hit) {
+  if (endstop_x_hit || endstop_y_hit || endstop_z_hit || endstop_z_probe_hit) {
     SERIAL_ECHO_START;
     SERIAL_ECHOPGM(MSG_ENDSTOPS_HIT);
     if (endstop_x_hit) {
       SERIAL_ECHOPAIR(" Z:", (float)endstops_trigsteps[Z_AXIS] / axis_steps_per_unit[Z_AXIS]);
       LCD_MESSAGEPGM(MSG_ENDSTOPS_HIT "Z");
     }
+    if (endstop_z_probe_hit) {
+    	SERIAL_ECHOPAIR(" Z_PROBE:", (float)endstops_trigsteps[Z_AXIS] / axis_steps_per_unit[Z_AXIS]);
+    	LCD_MESSAGEPGM(MSG_ENDSTOPS_HIT "ZP");
+    }
     SERIAL_EOL;
 
     endstops_hit_on_purpose();
           if(z_probe_endstop && old_z_probe_endstop)
           {
         	  endstops_trigsteps[Z_AXIS] = count_position[Z_AXIS];
-        	  endstop_z_hit=true;
+        	  endstop_z_probe_hit=true;
 
 //        	  if (z_probe_endstop && old_z_probe_endstop) SERIAL_ECHOLN("z_probe_endstop = true");
           }
           if(z_probe_endstop && old_z_probe_endstop)
           {
         	  endstops_trigsteps[Z_AXIS] = count_position[Z_AXIS];
-        	  endstop_z_hit=true;
+        	  endstop_z_probe_hit=true;
 //        	  if (z_probe_endstop && old_z_probe_endstop) SERIAL_ECHOLN("z_probe_endstop = true");
           }
           old_z_probe_endstop = z_probe_endstop;