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


Mocha execute sequentially and the setup is within a `before`, so should be ok to split.

However, you don't need that many `then` you can do it like this instead:
driver
. performTouchAction(...)
...
performTouchAction()

only if the action parameter depends from previous results you need the then.

Also when checking value you can use `should.become` e.g.: 
```js
driver
   .getElement(...).getValue().should.become(5)
   .getElement(...).getValue().should.become(6)
```
And use eventually to resolve the promise: e.g.. 

```js
driver
   .getElement().text().should.eventually.include
   .getElemen(...)
```

Also can use `Q.all()`
```
Q.all([
  el.getSize(),
  el.getLocation(),
]).spread(function (size, location) {
...
})
```