Add Radius to CandleSticks

[elliotaplant]

I have a design need to add a border radius to the candlesticks in the CandleStickSeries component. I see two ways of doing this:

1. Add a candleBorderRadius prop to the CandleStickSeries that gets passed along as rx and ry to the candle <rect />
2. Add wickProps and candleProps props to the CandleStickSeries that get passed along and spread on the wick and candle respectively.

I'll make two PR's with updates to the components and docs for anyone that wants to see the code in detail.

[rrag]

Thanks for the PRs, but I am not going to accept them for reasons mentioned in the PRs.

Thank you for your effort, sorry I could not merge it but
performance of candlestick chart is very important for me to compromise