XCOMMONS-442: Upgrade to Selenium 2.40
* Stop using Selenium Maven Plugin as it doesn't work with the latest version of Selenium.
* Fix package of WebDriverBackedSelenium.

(cherry picked from commit a2ea70f0d3e55912583c3776eafe9d71eb1cb40c)
[misc] Fix flickering test.

(cherry picked from commit 5060d7eefde42bd1870cbe250dfc0369afe3c74e)
[misc] Fix flickering test.

(cherry picked from commit 3902a5fd5cba3c04fef047dfe96f46667824573c)
[misc] Attempt to fix flickering test.

(cherry picked from commit 8478823fa894ba365a003c6c3a35954ba28d7981)