New report module. 6 persistent work coordinates. New G-codes and settings. README and minor bug updates

(NOTE: This push is likely buggy so proceed with caution. Just
uploading to let people know where we're going.)

- New report.c module. Moved all feedback functions into this module to
centralize these processes. Includes realtime status reports, status
messages, feedback messages.

- Official support 6 work coordinate systems (G54-G59), which are
persistently held in EEPROM memory.

- New g-code support: G28.1, G30.1 stores current machine position as a
home position into EEPROM. G10 L20 Px stores current machine position
into work coordinates without needing to explicitly send XYZ words.

- Homing performed with '$H' command. G28/G30 no longer start the
homing cycle. This is how it's supposed to be.

- New settings: Stepper enable invert and n_arc correction installed.

- Updated and changed up some limits and homing functionality. Pull-off
travel will now move after the homing cycle regardless of hard limits
enabled. Fixed direction of pull-off travel (went wrong way).

- Started on designing an internal Grbl command protocol based on the
'$' settings letter. Commands with non numeric characters after '$'
will perform switch commands, homing cycle, jogging, printing
paramters, etc. Much more to do here.

- Updated README to reflect all of the new features.

protocol.h

@@ -29,25 +29,6 @@
 // buffer.
 #define LINE_BUFFER_SIZE 50
 
-// Define Grbl status codes.
-#define STATUS_OK 0
-#define STATUS_BAD_NUMBER_FORMAT 1
-#define STATUS_EXPECTED_COMMAND_LETTER 2
-#define STATUS_UNSUPPORTED_STATEMENT 3
-#define STATUS_FLOATING_POINT_ERROR 4
-#define STATUS_MODAL_GROUP_VIOLATION 5
-#define STATUS_INVALID_STATEMENT 6
-#define STATUS_HARD_LIMIT 7
-#define STATUS_SETTING_DISABLED 8
-#define STATUS_SETTING_STEPS_NEG 9
-#define STATUS_SETTING_STEP_PULSE_MIN 10
-#define STATUS_SETTING_READ_FAIL 11
-
-// Define Grbl misc message codes
-#define MESSAGE_SYSTEM_ALARM 0
-#define MESSAGE_HOMING_ENABLE 1
-
-
 // Initialize the serial protocol
 void protocol_init();
 
@@ -61,10 +42,4 @@ uint8_t protocol_execute_line(char *line);
 // Checks and executes a runtime command at various stop points in main program
 void protocol_execute_runtime();
 
-// Prints Grbl's status messages.
-void protocol_status_message(uint8_t status_code);
-
-// Prints any misc messages.
-void protocol_misc_message(uint8_t message_code);
-
 #endif