Adb shell input roll

Implementation for #737
This is probably not the final implementation. Making a pull request to open a discussion.

The implementation works for me using selendroid-standalone.

Here's the code how to use it:

- activate something scrollable/rollable (it might be a spinner)
- call `getSelendroidDriver().getTrackBall().roll(1, 5);`

this would roll the list and select the 5th item. First 'roll' attempt might not actually roll anything depending on number of items displayed.

I am not sure about the `selendroid-server` changes. They might not have been necessary and I haven't tested them.

Any thoughts?
the reason things like TouchScreen are exposed is to use them in the Actions / TouchActions api.

I think we should probably just expose the 'roll' command directly here instead for now?

The only thing I could think of where this would be beneficial is if the Mouse interface had some sort of scrolling in the main Selenium project... but it doesn't. So we couldn't use the Actions api there.