Updating IE driver to use correct parameter in message loop for executing asynchronous JavaScript.

Fixes issue #5137.
Enabled synthetic events mouse clicks to work even if the click triggers alerts.
Fixing up .NET tests.
Implementing support for List<WebElement> in AjaxElementLocator
(On behalf of JensHausherr) Fixing Context-Type header in responses returned by HubStatusServlet, ProxyStatusServlet and TestSessionStatusServlet
Implementing an option in SauceDriver to allow setting requireWindowFocus capability
Catching up.
Merge branch 'master' of https://github.com/SeleniumHQ/selenium
Second batch of changes for py2.6 and py3 concurrent support