Add wrapper script for lcd.py.

The wrapper script also does some sanity checks for my Pi setup.

wrappers/lcd

+#!/bin/sh
+
+PYTHONPATH="/home/pi/Adafruit-Raspberry-Pi-Python-Code/Adafruit_CharLCDPlate"
+export PYTHONPATH
+
+# When switching the CharLCDPlate for an 8x8 LDE matrix,
+# both boards use an MCP23017 I2C chip with the address hardwired to 0x20.
+# To avoid writing garbage to the LED matrix, we make sure that the device
+# looks like a CharLCDPlate:
+if ! i2cget -y 1 0x20 0x13 | grep -q '^0xff$' # GPIOB input register on power on
+then
+	if ! i2cget -y 1 0x20 0x00 | grep -q '^0x3f$' # IODIRA register after Adafruit_CharLCDPlate init
+	then
+		echo "Not a LCD Pi Plate (based on heuristics)." >&2
+		exit 0
+	fi
+fi
+/usr/bin/python /home/pi/lcdtools/lcd.py "$@"