Update Chromedriver to 2.38 to support Chrome v66

Also update LatestTestedChromeVersion to 66.

Note: With Chrome v66, there was a change in the Window Structure, breaking the Lookup of the Chrome Windows in the "ChromeBrowserContentLocator", needed for the Screenshot Automation. Fixing that, breaks the Lookup for Chrome v65 and lower Versions.

Therefore, ScreenshotAutomation is currently only supported for Chrome v66 and upwards.