Fix #386 - Arduino compiling problem

The core fix was to remove the redundant includes of grbl.h
from the individual spindle.cpp files.  Since those files
are inlined into Grbl_Esp32.ino via nested includes, the
top level include of grbl.h in the .ino covers them.

I also did some cleanups:
- renaming tools/ to Spindles/ .  While "tools" is a good
   name in the CNC domain, meaning "toolheads", in the
   software domain it typically means "ancillary programs
   used for building the software"
- Added a "#pragma once" to grbl.h just in case; it had
   no header guard.
- Removed a duplicate #include grbl.h from stepper.cpp
- Deleted some trailing whitespace
- Fixed missing newline at the end of some files

Grbl_Esp32/Grbl_Esp32.ino

@@ -21,7 +21,7 @@
 #include "grbl.h"
 #include "WiFi.h"
 
-#include "tools/SpindleClass.cpp"
+#include "Spindles/SpindleClass.cpp"
 
 // Declare system global variable structure
 system_t sys;

Grbl_Esp32/Spindles/BESCSpindle.cpp

@@ -38,9 +38,6 @@
 
 */
 
-#include "grbl.h"
-#include "SpindleClass.h"
-
 // don't change these
 #define BESC_PWM_FREQ           50.0f // Hz
 #define BESC_PWM_BIT_PRECISION  16   // bits

Grbl_Esp32/Spindles/DacSpindle.cpp

@@ -22,9 +22,6 @@
 
 */
 
-#include "grbl.h"
-#include "SpindleClass.h"
-
 // ======================================== DacSpindle ======================================
 void DacSpindle :: init() {
     get_pins_and_settings();

Grbl_Esp32/Spindles/HuanyangSpindle.cpp

@@ -44,8 +44,6 @@
         Add periodic pinging of VFD in run mode to see if it is still at correct RPM
 */
 
-#include "grbl.h"
-#include "SpindleClass.h"
 #include "driver/uart.h"
 
 #define HUANYANG_ADDR           0x01

Grbl_Esp32/Spindles/Laser.cpp

@@ -20,9 +20,6 @@
 
 */
 
-#include "grbl.h"
-#include "SpindleClass.h"
-
 // ===================================== Laser ==============================================
 
 

Grbl_Esp32/Spindles/NullSpindle.cpp

@@ -19,8 +19,6 @@
     along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
 
 */
-#include "grbl.h"
-#include "SpindleClass.h"
 
 // ======================= NullSpindle ==============================
 // NullSpindle is just bunch of do nothing (ignore) methods to be used when you don't want a spindle

Grbl_Esp32/Spindles/PWMSpindle.cpp

@@ -19,8 +19,6 @@
     along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
 
 */
-#include "grbl.h"
-#include "SpindleClass.h"
 
 // ======================= PWMSpindle ==============================
 /*

Grbl_Esp32/Spindles/RelaySpindle.cpp

@@ -19,8 +19,6 @@
     along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
 
 */
-#include "grbl.h"
-#include "SpindleClass.h"
 
 // ========================= RelaySpindle ==================================
 /*

Grbl_Esp32/Spindles/SpindleClass.cpp

@@ -32,8 +32,6 @@
         SPINDLE_DIR_PIN
 
 */
-#include "grbl.h"
-#include "SpindleClass.h"
 #include "NullSpindle.cpp"
 #include "PWMSpindle.cpp"
 #include "DacSpindle.cpp"
@@ -95,5 +93,3 @@ void Spindle :: spindle_sync(uint8_t state, float rpm) {
     protocol_buffer_synchronize(); // Empty planner buffer to ensure spindle is set when programmed.
     set_state(state, rpm);
 }
-
-

Grbl_Esp32/Spindles/SpindleClass.h

@@ -38,7 +38,7 @@
 #ifndef SPINDLE_CLASS_H
 #define SPINDLE_CLASS_H
 
-#include "grbl.h"
+#include "../grbl.h"
 #include <driver/dac.h>
 #include "driver/uart.h"
 

Grbl_Esp32/grbl.h

@@ -18,6 +18,7 @@
   along with Grbl.  If not, see <http://www.gnu.org/licenses/>.
 */
 
+#pragma once
 // Grbl versioning system
 
 #define GRBL_VERSION "1.2a"
@@ -53,7 +54,7 @@
 #include "protocol.h"
 #include "report.h"
 #include "serial.h"
-#include "tools/SpindleClass.h"
+#include "Spindles/SpindleClass.h"
 #include "stepper.h"
 #include "jog.h"
 #include "inputbuffer.h"

Grbl_Esp32/stepper.cpp

@@ -1,5 +1,3 @@
-#include "grbl.h"
-
 /*
   stepper.c - stepper motor driver: executes motion plans using stepper motors
   Part of Grbl