First pass at iOS touch for Appium 1.0

This implements touch and a slightly simplified version of multitouch for iOS. It does not handle well when there is no correspondence in timing for multi-finger gestures. To get that working should not be a huge amount of work, it's just a matter of filling in waits when gestures are not in sync. As well as finding some case in which to test them!

The wire protocol does not specify an endpoint for these gestures, so I've just sent them on `perform()`.

The spec: 
https://dvcs.w3.org/hg/webdriver/raw-file/tip/webdriver-spec.html#touch-gestures
https://dvcs.w3.org/hg/webdriver/raw-file/tip/webdriver-spec.html#multiactions-1

@jlipps