Update connection logic to append to the X-Forwarded-For header if it is present
Fixed style check issue
Fixed join issue when building the X-Forwarded-For value
Added the parameter `reuseXForwarded` to the `ProxyHandler` class. This allows any existing X-Forwarded-For header to be appended to. It is turned off by default thus the X-Forwarded-For header is overwritten unless it is desired not to. Also, remove the X-Forward* logic from HttpClientConnection and SpdyClientConnection.
Removed unused imports to pass CheckStyle