New EEPROM restore functions.

- Tweaked the previous EEPROM restore implementation and added new
functionality.

- `$RST=$` restores the `$$` grbl settings back to firmware defaults,
which are set when compiled.

- `$RST=#` restores the `$#` parameters in EEPROM. At times it’s useful
to clear these and start over, rather than manually writing each entry.

-`$RST=*` wipe all of the data in EEPROM that Grbl uses and restores
them to defaults. This includes `$$` settings, `$#` parameters, `$N`
startup lines, and `$i` build info string.

NOTE: This doesn’t write zeros throughout the EEPROM. It only writes
where Grbl looks for data. For a complete wipe, please use the Arduino
IDE’s EEPROM clear example.

- Refactored the restore and wipe functions in settings.c to
accommodate the new commands.

doc/log/commit_log_v0.9i.txt

@@ -1,3 +1,9 @@
+----------------
+Date: 2015-06-18
+Author: Sonny Jeon
+Subject: Updated README
+
+
 ----------------
 Date: 2015-06-18
 Author: Sonny Jeon