cc @imurchie @dpgraham @mykola-mokhnach @KazuCocoa .

This represents my vision for how clients should expose the template matching functionality with opencv. I.e., return a "clone" of WebElement with a smaller set of methods, so users can imagine they are simply finding "elements" and clicking on them.

Note that tests will only pass with appium/appium-support#74 applied to the Appium server used for testing.