Updating chromedriver executable download location
Refactored .NET DriverService-based shutdown code.

Moved waiting for the driver service process to end to immediately after
sending the shutdown HTTP request. Waiting to catch the exception for a
failed HTTP request due to a closed socket is very expensive. This cuts
shutdown time for a driver service executable to about 33% of what it used
to be for the IE driver, with larger savings for Chrome and PhantomJS.
Fixes issue #6425.
Updating .NET assembly version numbers and CHANGELOG for 2.37.0 release
Updating IE prebuilts for 2.37 release
Bumping version of Firefox extension for 2.37 release