Expose webdriver wait functionality

[xeqi]

Create wait-until and implicitly-wait functions for the driver.

Not all functionality is exposed. I imagine testing something like sleep in miliseconds would be ugly, though perhaps a mock would work since its calling a java object.

[semperos]

I've been reviewing all the "wait" functionality provided by WebDriver. For WebDriverWait, I think we should support the three-member constructor at a minimum, which allows setting both a timeout and an interval for attempts. I'm not convinced that the five-member constructor adds much value, but I'm open to discussion on that point.

[semperos]

I created conflicts with some subsequent edits before merging this request. Thank you very much for adding this functionality and for adding tests for it. Merged.