Update Adafruit_CharLCDPlate/Adafruit_CharLCDPlate.py

A few changes relating to incorrect comments in cursors on and off
Added toggle cursor states

Main question concerns attempt to read information off the LCD as mentioned on pg. 24 and 58 of the specs in HD44780.pdf. 
The routine I've written does not work. Not sure if I don't understand the 
specs properly. Need help here.