0.9.x touch_ios7 should not force an orientation when orientation is 'unknown'

### previous behavior

the `device_orientation()` function returns `unknown` _if and only if_

1. the command is run on the iOS Simulator
2. the simulator has not been rotated since it was launched

the `touch_ios7()` function must translate the touch coordinates for orientations other than `down`.

if the orientation was `unknown`, the `touch_ios7()` function was forcing the orientation to `down` so that the touch coordinates were guaranteed to be correct.

### the problem

this is not desirable behavior because it causes an unnatural rotation - one that the user would never do.

### new behavior

the `touch_ios()` function will now only translate touch coordinates for these orientations:

* `left`
* `right`
* `up`

if the device orientation is `unknown`, the touch coordinates will not be translated.  

this new behavior could cause problems for some users.

### potential problems

the simulator will launch in the orientation that it was last in.  

this can lead to cases were a Scenario leaves the simulator in a particular orientation - you can visually see that the simulator is rotated to the orientation - but the `device_orientation()` function returns `unknown`.

on iOS 7, subsequent steps that use `touch` will fail because the touch coordinates will not be translated.

if you find yourself in this position, the work around is simple.

call `rotate_home_button_to({up|down|left|right})` before the touch, in the `Background`, or in a `Before` hook.

### related

* [new orientation route #22](https://github.com/calabash/calabash-ios-server/pull/22)
* [@driis support for iOS 7 rotation 213](https://github.com/calabash/calabash-ios/pull/213)
* [rotation when orientation is 'face up' or 'face down' 218](https://github.com/calabash/calabash-ios/pull/218)