Add a high, low, and average value display option on the monthly historic price chart

It would be useful to see the price of a game per month in terms of the following:

Per month:

1. Show the highest price sold
2. Show the lowest price sold
3. Show the average price

This is like a stock market candlestick chart without the beginning value and ending value.  It would look something like a cross instead of a candlestick with a body.  The reason is because the average price doesn't tell you everything.  We still want to see what the highest price and lowest price sold was in any given month.