Fix swipe action with target element: #3647

@Jonahss @imurchie (this reviewers of the first merge request that I closed because the new changes are a lot different) 

*  The original scope of this change was adding the ability to specify a destination element when doing a swipe.  Those are the changes you'll see in the server JS.
*  I added a bunch of tests.
*  When I started expanding the test suite for Android, I uncovered some nasty bugs w relative coordinates.  At least one was caused by copy/pasting.  I then discovered similar code (not nec buggy, but using the same patterns) in multiple places in the project.  I consolidated the logic to decrease the likelihood of bugs and ensure that absolute coordinates were all derived in the same way.
*  There's a bunch of spaghetti code.  If you have any suggestions on how I can get rid of it, lmk.
*  There's a change to the sample code that goes along with this.
*  I ran all the Android `touch` tests and they passed, with the exception of 'should work like `longPress` when released after a pause', which also failed for me before the refactoring


Yeah, it sucks. I'm just not groking how to get custom behavior
without breaking stuff.

On 10/31/14, Jonah <notifications@github.com> wrote:
>> +        contentElPos.y = y + hOffset;
>> +      })
>> +      .elementByName("Animation")
>> +      .then(function (el) {
>> +        animationEl = el;
>> +        return animationEl;
>> +      })
>> +      .getLocation()
>> +      .then(function (loc) {
>> +        animationElPos.x = contentElPos.x;
>> +        animationElPos.y = loc.y + hOffset;
>> +        delta.x = 0;
>> +        delta.y = animationElPos.y - contentElPos.y;
>> +        return contentEl;
>> +      })
>> +
>
> Maybe all the above logic can be moved into functions? This test is hard to
> read.
>
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