change MtxOrb kyboard mapping code to use KeyMap_<X>=<name>

LCDd.conf

@@ -643,14 +643,15 @@ Speed=19200
 # Set the display type [default: lcd; legal: lcd, lkd, vfd, vkd]
 Type=lkd
 
-# The following table translate from MtxOrb Key to Logical Key.
-# See [menu] section for an explanation of the key mappings
-LeftKey=A
-RightKey=B
-EnterKey=C
-UpKey=D
-DownKey=E
-EscapeKey=F
+# The following table translates from MtxOrb key letters to logical key namess.
+# By default no keys are mapped, meaning the keypad is not used at all.
+#KeyMap_A=Left
+#KeyMap_B=Right
+#KeyMap_C=Up
+#KeyMap_D=Down
+#KeyMap_E=Enter
+#KeyMap_F=Escape
+# See the [menu] section for an explanation of the key mappings
 
 # You can find out which key of your display sends which
 # character by setting keypad_test_mode to yes and running