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


Dunno. It was already there.

On 10/31/14, Jonah <notifications@github.com> wrote:
>> @@ -50,10 +133,11 @@ describe('testapp - touch actions', function () {
>>          .then(function (el) {
>>            return driver.performTouchAction((new TouchAction())
>>              .press({el: el}).moveTo({el: el, x: 0, y: 100 }).release());
>> -        }).sleep(5000)
>> +        })
>> +        .sleep(5000)
>
> Whats the sleep for? Can we do a waitFor?
>
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