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


I'd like to.  But I need to ensure there aren't any resets between
tests. I also want to ensure the order is deterministic.
  @sebv Do you have a recommendation on how I can do that? It looks
like the order is always the same, so that's probably not an issue.
The resets are my main concern. Every time I tried breaking them up,
things got wonky.

On 10/31/14, Jonah <notifications@github.com> wrote:
>> +        .then(function () { return slider.getAttribute("value"); })
>> +        .then(testSliderValueNear50)
>> +
>> +        // test: press {x, y}, moveTo {destEl}
>> +        .then(function () {
>> +          return driver.performTouchAction((new TouchAction())
>> +            .press({x: centerPos.x, y: centerPos.y}).wait({ms:
>> 500}).moveTo({el: destEl}).release());
>> +        })
>> +        .then(function () { return slider.getAttribute("value"); })
>> +        .then(function (valueAfter) {
>> +          valueAfter.should.equal("100%");
>> +        })
>> +
>> +        .nodeify(done);
>> +    });
>> +
>
> Wowza. Can these all be broken into separate tests?
>
> ---
> Reply to this email directly or view it on GitHub:
> https://github.com/appium/appium/pull/3943/files#r19697363