Web view add console.log support

console.log support WebView.swift

let jsContext = mainWebview.mainFrame.javaScriptContext

jsContext.evaluateScript("var console = {log: function () {var message = '';for (var i = 0; i < arguments.length; i++) {message += arguments[i] + ' '};console.print(message)},warn: function () {var message = '';for (var i = 0; i < arguments.length; i++) {message += arguments[i] + ' '};console.print(message)},error: function () {var message = '';for (var i = 0; i < arguments.length; i++){message += arguments[i] + ' '};console.print(message)}};")

let logFunction: @convention(block) (NSString!) -> Void = { (message:NSString!) in
  print("JS: \(message)")
}

jsContext.objectForKeyedSubscript("console").setObject(unsafeBitCast(logFunction, AnyObject.self), forKeyedSubscript:"print")